Name: measuring voltage, current, and resistance
Uploaded: 2023-04-30T06:39:57.000Z
Duration: 12 min 41 s
Channel: JoVE

K12 Standards

Arizona Science Standards

High School

Physical Science

HS+Phy.P4

HS+Phy.P4U1.8

investigation-ohm-s-law-for-ohmic-and-nonohmic-conductors

Investigation Ohm's Law for Ohmic and Nonohmic Conductors

1. 熟悉仪器装置
<ol>
	<li>本实验需使用计算机采集数据并绘制图表。</li>
	<li>通过双击计算机桌面上的“欧姆定律”图标来启动实验软件。程序加载后，屏幕应显示一个图表、一个数据表，以及位于右下角的电压和电流读数框。</li>
	<li>点击“零点”按钮，并选择“归零所有传感器”，以确保电压和电流传感器在未连接时读数为零。</li>
	<li>根据图1中的电路图，将电压传感器的两根导线连接到电源（一个蓝色盒子）。红色导线接电源的+端，黑色导线接-端。</li>
	<li>确保电流传感器尚未连接，并将电源上的电流调节旋钮调至最大（完全顺时针方向）。</li>
	<li>在计算机上点击绿色箭头图标（“采集”按钮）以开始数据采集。</li>
	<li>观察当电源上的电压旋钮从最小值调节到最大值时发生的现象。调节该旋钮可使电压从约+0.7 V变化至至少+5 V。</li>
	<li>将电压传感器的导线反接（红色接-端，黑色接+端），然后重复步骤1.5–1.7。此时，调节旋钮可获得约−0.7 V至-5 V的电压范围。因此，通过调节电源电压并反接导线，本实验可使用接近-5 V至+5 V的完整电压范围。需注意，本实验所用电源无法输出低于0.7 V的电压（此为不常见特性），但现有范围已足以确定所需研究的物理关系。</li>
</ol>
<img alt="显示电源和电压传感器测量电势差的电路图。" src="/files/ftp_upload/10116/10116fig1.jpg" data-altupdatedat="1761830439000" data-alt="图 1">
图1：该电路图显示了电源（用+和-符号标记）和电压传感器（V）通过两根导线连接。
2. 探究欧姆定律
注意：本实验部分的目标是观察电流与电压关系的曲线图。
<ol>
	<li>要更改坐标轴上显示的内容，请单击坐标轴标签，勾选相应的选项以显示所需信息，并（仅针对 y 轴）取消勾选不需要显示的项目。将图形设置为在 y 轴上显示电流，在 x 轴上显示电势。</li>
	<li>为正确设置坐标轴刻度，请单击 y 轴左侧的任意一个数值，弹出设置框后，手动输入最小值为 -0.3，最大值为 0.3。对 x 轴重复此操作：单击 x 轴下方的任意一个数值以调出设置框，输入最小值为 -6，最大值为 6。这样可使图形显示 -0.3 至 +0.3 A 之间的电流，以及 -5 V 至 +5 V 之间的电压。</li>
	<li>根据图 2中的电路图，连接电路以测量通过 100 Ω 电阻的电压和电流。</li>
	<li>使用电阻箱作为电阻，将其阻值设为 100 Ω。在电源上，将电流和电压均调至最大。</li>
	<li>按下绿色箭头图标以开始数据采集。</li>
	<li>在数秒内将电压调至最小，然后迅速在电源端反转导线连接。再在数秒内将电压旋钮重新调向最大。这将得到一条从约 -5 伏到 +5 伏的电流-电压关系图。</li>
	<li>重复该过程直至获得满意的图形，然后选择“数据”菜单，并点击“存储最新运行”。</li>
	<li>观察电流-电压关系图呈一条直线。点击回归按钮对数据进行线性拟合，并记录直线的斜率。
	<ol>
		<li>图 4 显示了标称为 100 Ω 电阻的电流-电压关系图。对数据进行线性拟合后得到的斜率为 0.00991 A/V。该电阻倒数为 0.0100 A/V，与测得的斜率吻合良好。</li>
	</ol>
	</li>
	<li>将电阻箱的阻值改为 200 Ω，并重复步骤 2.6–2.9。</li>
	<li>比较两条直线的斜率值与对应的电阻值，确定电流、电压与电阻之间的关系。
	<ol>
		<li>图 5 显示了标称为 200 Ω 电阻的电流-电压关系图。对数据进行线性拟合后得到的斜率为 0.00510 A/V。该电阻倒数为 0.00500 A/V，与测得的斜率吻合良好。</li>
	</ol>
	</li>
	<li>电流-电压关系图的斜率恰好等于电阻的倒数。这可以表示为： 
	<img alt="欧姆定律公式 I=ΔV/R，说明电路中的电流流动。" src="/files/ftp_upload/10116/10116eq1.jpg" data-altupdatedat="1761830439000" data-alt="公式 1"> 或 <img alt="欧姆定律公式 ΔV=IR，基本电路原理，电压与电流的关系" src="/files/ftp_upload/10116/10116eq2.jpg" data-altupdatedat="1761830439000" data-alt="公式 2">
	<ol>
		<li>电源输出的电流与电压成正比，与电阻成反比。当电流作为电压的函数作图时，直线的斜率应等于电阻的倒数。</li>
	</ol>
	</li>
</ol>
 
<img alt="用于测量电流和电压的带有电阻器、电流表和电压表的电路。" src="/files/ftp_upload/10116/10116fig2.jpg" data-altupdatedat="1761830439000" data-alt="图 2"> 
图 2：该电路图显示电源连接至一个 100 Ω 电阻器，电压传感器（V）测量电阻器两端的电势差，电流表测量通过电阻器的电流。
 
 <img alt="电路图；电流表、电压传感器；测量电流和电压；用于教学。" src="/files/ftp_upload/10116/10116fig3.jpg" data-altupdatedat="1761830439000" data-alt="图 3"> 
图 3： 在此电路图中，电阻器被替换为一个灯泡，并增加了一个开关。开关初始状态为断开，因此实验开始时灯泡处于关闭状态。 
<img alt="线性伏安法曲线，显示电流与电势的关系；电化学分析数据。" src="/files/ftp_upload/10116/10116fig4.jpg" data-altupdatedat="1761830439000" data-alt="图 4"> 
图 4： 电流与电压关系图，使用标称为 100 Ω 的电阻器。对数据进行线性拟合得到的斜率为 0.00991 A/V。请注意，图中心区域数据缺失仅仅是本实验所用电源的特性所致，该电源具有无法输出约 0.7 V 以下电压的特殊性质。<img alt="线性 I-V 曲线；电流-电势关系；电化学；数据分析；科学图表。" src="/files/ftp_upload/10116/10116fig5.jpg" data-altupdatedat="1761830439000" data-alt="图 5"> 
图 5： 电流与电压关系图，使用标称为 200 Ω 的电阻器。对数据进行线性拟合得到的斜率为 0.00510 A/V。
3. 研究灯泡
<ol>
	<li>将前一个电路中的电阻器替换为一个小的白炽灯泡（图3）。重复实验，获得灯泡的电流随电压变化的曲线图。注意灯泡的曲线图与电阻器相比在形式上的任何差异。
	<ol>
		<li>图6 显示了白炽灯泡的电流-电压关系图。总体而言，电流随电压升高而增加，但该曲线远不如电阻器的曲线线性。该图还显示，当电压上升时，在给定电压下的电流通常高于电压下降至相同电压时的电流值。</li>
	</ol>
	</li>
	<li>现在，改为绘制电流随时间变化的曲线，而非电流随电压变化的曲线。为此，点击横轴上的“voltage”标签，调出图形可绘制变量的列表，并选择“time”代替“voltage”。</li>
	<li>调高电压，使灯泡明亮发光，然后使用电源开关关闭电源。点击屏幕上的“Collect”按钮（绿色箭头）开始数据采集，再重新打开电源。
	<ol>
		<li>观察 图7 所示的曲线图。当电源接通时，通过灯泡的电流先迅速升至较高水平，随后下降至一个较小的恒定值。这与标准电阻器的行为明显不同，标准电阻器通常在电源接通时直接跃升至一个恒定值。</li>
		<li>上述两种现象的解释相同：灯泡灯丝的温度越高，其电阻越大。当灯泡关闭时（图7），灯丝处于室温，电阻相对较低。当灯泡开启时，由于电阻较低，电流迅速上升；但随着灯丝温度升高，电阻增大，电流随之下降。最终，温度趋于稳定，电流也保持恒定。</li>
		<li>当电压上升时（图6），灯丝正在升温，此时灯丝较冷，电阻较低，因此电流较高。在曲线图的后半段，当电压降低时，灯丝从较高温度逐渐冷却，因此电阻较高，电流较低。</li>
	</ol>
	</li>
	<li>最后，切换回电流-电压关系图，并用一个发光二极管（LED）代替灯泡。</li>
	<li>与之前类似，获得LED的电流随电压变化的曲线图。务必同时使用正电压和负电压，以观察LED在电路中行为的完整范围。
	<ol>
		<li>图8 显示了LED的电流-电压关系图。当电压为负时，二极管不允许电流通过；但当电压为正且超过某一阈值时，电流开始流动，并随电压的升高迅速增加。因此，二极管相当于一个电流的单向阀。注意，灯泡灯丝和电阻器均无此类方向性特征。</li>
	</ol>
	</li>
</ol>
<img alt="显示电流与电位关系的循环伏安法图谱，用于电化学分析。" src="/files/ftp_upload/10116/10116fig6.jpg" data-altupdatedat="1761830439000" data-alt="图6"> 
图6： 白炽灯泡的电流与电压关系图。图中曲线从左下角开始，随着电压升高沿上侧轨迹上升，灯泡变得非常明亮；随后电压降低，曲线沿下侧轨迹返回至左下角。
<img alt="显示电流随时间变化的电化学实验图，说明瞬态电流响应。" src="/files/ftp_upload/10116/10116fig7.jpg" data-altupdatedat="1761830439000" data-alt="图 7"> 
图 7：白炽灯泡的电流-时间关系图。灯泡初始处于关闭状态，随后在约1.4秒处接通电压并保持恒定。电流峰值达到约0.57 A，之后下降并稳定在约0.27 A的恒定值。
<img alt="电化学分析图；显示电流与电位关系的I-V曲线；伏安法。" src="/files/ftp_upload/10116/10116fig8.jpg" data-altupdatedat="1761830439000" data-alt="图8"> 
图8：二极管的电流-电压关系图。从某种意义上说，二极管的作用类似于电流的单向阀。当电压为负时，二极管不允许电流通过；而当电压为正且超过某一阈值时，电流开始流动，并随着电压在单一方向上的增加而迅速增大。

在当今世界，电子设备无处不在，而欧姆定律在这些设备中均发挥着重要作用。例如，设计为使用两节1.5伏电池串联（总电压为3伏）工作的手电筒，必须配备具有适当电阻的灯泡，以使电池提供适量的电流，让灯泡明亮发光，同时避免烧毁。欧姆定律有助于指导这种灯泡的选择。
另一种应用是三档调光灯泡，可发出三种不同亮度的光。实现这种灯泡的一种方法是使用单根灯丝，根据所需的亮度，将电压施加在灯丝的不同部分。同样，欧姆定律在确定电压所施加的灯丝比例以及整个灯丝的电阻方面起着重要作用。
欧姆定律的另一个应用是限制供给特定设备的电流，以降低触电风险，或保护设备本身（过高的电流可能导致设备过热甚至烧毁）。欧姆定律告诉我们，在给定电压下，电阻越大，电流越小，因此可通过串联一个较大的电阻来限制设备中的电流。

欧姆定律在欧姆与非欧姆导体中的研究

来源：Andrew Duffy，博士，波士顿大学物理系，马萨诸塞州波士顿
本实验研究欧姆定律，该定律描述了电流、电压和电阻之间的关系。
本实验的一个目标是熟悉电路图以及基本电路中涉及的术语，例如电阻器、电阻、电流、电压和电源。通过完成本实验，将掌握如何连接电路，以及如何测量流经电路元件的电流和其两端的电势差（即电压）。
在电路中，电池或电源提供以伏特（V）为单位测量的电压，从而驱动电荷流动。电路中的其他元件，例如灯泡或电阻器（通常只是绕成线圈的细长导线），会限制电荷流动的速率。电荷流动的速率称为电流，以安培（A）为单位，简称安；电阻器和灯泡灯丝对电流的阻碍程度称为电阻，以欧姆（Ω）为单位。本实验涉及对欧姆定律的探究，该定律描述了电压、电流和电阻之间的关系。
本实验还探讨了一种基本电路元件——电阻器，与灯泡以及发光二极管（LED）之间的差异。灯泡和发光二极管广泛应用于多种常见设备中，用于各类照明用途，因此了解其工作原理具有重要意义。

来源：Andrew Duffy，博士，美国马萨诸塞州波士顿市波士顿大学物理系  
本实验研究欧姆定律，该定律描述了电流、电压……之间的关系

欧姆定律描述了电路或电气元件的电压、电流和电阻之间的关系。电压 V、电流 I 和电阻 R 是所有电子设备（如收音机、音乐播放器和计算机）以及更简单的电气应用（如房屋布线、保险丝盒和家庭照明）运行的基本要素。在所有这些情况下，电路的行为都具有可预测性，能够进行合理设计，这都得益于欧姆定律。本视频将介绍电路术语、符号和电路图，然后演示如何连接一个简单电路。此外，还将测量通过元器件的电流以及元器件两端的电压。电源或电池的输出端包含正极和负极，分别定义了称为电势的物理量的高值和低值。这种电势之间的差异即为电压，单位为伏特（volts）。如需进一步了解这些术语，请参阅本系列中关于电势的视频。电路是由相互连接的元件组成的网络，用于实现特定功能。电流是指每秒通过的电荷量，单位为安培（简称安）。有趣的是，在电路中只有带负电荷的电子会在导线中移动。由于电子带负电，其流动方向与电流方向相反。电流只能在形成闭合回路的导线和元件中流动，这类似于水从水库流出，经过水泵进入水轮机，再流回水库的循环过程。在一定程度上，所有电气元件都会阻碍电流的流动，就像管道中的瓶颈会减少水流一样。这种现象称为电阻，其单位为欧姆（ohms）。欧姆定律将电阻定义为元件两端的电压除以通过该元件的电流。对于专门称为电阻器的元件，其电阻值近似为常数。普通电路板上的电阻器通常是一个小型圆柱形物体，其表面带有表示电阻值的色环编码。根据欧姆定律，通过恒定电阻的电流与所施加的电压成正比，与电阻成反比。实际上，大多数材料的电阻通常随温度升高而增加。某些器件（如二极管）的电阻也会随工作条件（即电压和电流）以及其他因素而变化。二极管是一种近似只允许电流单向通过的器件。因此，它表现为一个单向阀，在“正向”时以极低的电阻通过电流，而在“反向”时则以极高的电阻阻止电流通过。发光二极管，也称为“LED”，是一种在正向电流通过时会发光的二极管。与普通二极管类似，LED 在反向电压下不导通电流，此时不会发光。根据电压、电流和电阻之间的简单关系，欧姆定律（通常表示为 V 等于 I 乘以 R）使得在已知其中两个量的情况下，可以计算出第三个量。本视频将展示如何轻松测量元件两端的电压及其通过的电流。这些实验还将演示不同电路中的欧姆定律，并说明电阻、灯泡和发光二极管的电流与电压之间的关系。测量装置由电压传感器、电流传感器、电源、计算机控制的测量系统以及待测组件组成。要启动测量软件，请双击计算机桌面上的“Ohm's Law”图标。程序加载后，屏幕应显示一个图表、一个表格，以及在左下角显示电压和电流测量值的数值框。单击“归零”按钮，然后选择“归零所有传感器”，以消除数据采集系统中的偏移量。当设备的导线未连接任何物体时，电压和电流读数应为零。通过单击坐标轴标签并勾选所需选项来选择将要绘制的数据。对于 y 轴，取消勾选不需绘制的项目。将图形设置为在 y 轴上显示电流，在 x 轴上显示电压。接下来，将 y 轴刻度设置为负 0.3 至正 0.3 安培，并将 x 轴刻度设置为负 5 至正 5 伏特。在第一个实验中，使用一个可设置不同阻值的电阻箱，以观察电阻器的电流随电压的变化情况。将电阻箱设置为 100 欧姆。然后按照电路图所示，将电源、电压传感器、电流传感器和电阻箱连接在一起。最后，将电源的电流和电压输出均设置为最大值。单击绿色箭头图标以开始数据采集。缓慢将电源电压降低至最小值。然后，调换电源端的导线连接，并缓慢将电压重新增加至最大值。这将得到一幅从 -5 到 +5 伏特范围内的电流-电压关系图。重复此过程，直至图形无噪声，然后保存数据。对于 100 欧姆的电阻，电流与电压的关系曲线是一条直线。对数据进行线性拟合，并记录直线的斜率。该斜率应非常接近 0.0100 安/伏，即电阻的倒数。现在将电阻箱设置为 200 欧姆，并重复实验，以获得 -5 至 +5 伏电压范围内另一条电流随电压变化的曲线。此时斜率应非常接近 0.00500 安/伏，同样等于电阻的倒数。对于恒定电阻，欧姆定律指出，通过电阻器的电流与所加电压成正比，与电阻成反比。这一点在100欧姆和200欧姆电阻器的数据中均明显可见。在下一个实验中，将电阻箱替换为一个小型白炽灯泡，如示意图所示。将电源上的电压控制调至最大值，然后开始数据采集。缓慢降低电压至最小值，再缓慢将电压升高至最大值。计算机会显示约 +0.7 至 +5 伏特范围内的电流随电压变化的曲线图。反转电源引线，将电压控制调至最大值，然后重复将电压从最小值逐渐增加至最大值的过程。计算机会显示约 -0.7 至 -5 伏特范围内的电流-电压关系图。对于灯泡而言，电流与电压关系曲线远不如电阻的线性关系明显。该图还显示，当电压升高时，在给定电压下的电流通常高于电压降低时在同一电压下的电流。当电压升高时，灯丝逐渐升温。若灯丝起始温度较低，则其电阻较小，电流较大。当电压降低时，灯丝从较高温度开始冷却，因此在相同工作点下具有较高的电阻和较低的电流。现在将电流与电压的关系图改为电流与时间的关系图。为此，将横轴更改为测量时间。将电压调至最大，使灯泡明亮发光。然后关闭电源。单击绿色箭头以开始数据采集，随后重新打开电源。电源刚接通时，流经灯泡的电流较大，随后下降至一个较低且恒定的值。当灯泡未点亮时，灯丝处于室温，具有相对较低的电阻。当灯泡刚开启时，由于电阻较低，电流会迅速升至较高水平。然而，灯丝的电阻随温度显著增加——随着灯丝加热，电阻增大，电流随之下降。最终，其温度趋于稳定，电流也保持恒定。最后，将坐标轴重新设置为显示电流与电压的关系，并用发光二极管（“LED”）替代灯泡。普通LED的最大电流约为30 mA，因此必须仔细监测电流，以防LED烧毁。使用先前实验中的步骤，获取发光二极管（LED）的电流随电压变化的曲线图。首先在LED两端施加正向电压，并将电源电压从最大值调节至最小值。然后交换电源引线，将电压从最小值重新调节至最大值，以观察LED的单向导通特性。结果图显示，只有当电压为正且大于某一阈值时，发光二极管（LED）才允许电流通过。一旦二极管“导通”，随着电压升高，电流迅速增加。然而，在负电压下没有电流流过。这种特性表明，LED 的作用类似于电流的单向阀。在当今世界，电子设备无处不在，而欧姆定律在每一台电子设备中都发挥着重要作用。例如，手电筒中的灯泡设计为使用两节1.5伏电池串联供电。因此，必须选择具有合适电阻的灯泡，以使电池提供适量的电流，使灯泡明亮发光，同时避免烧毁。欧姆定律有助于指导灯泡的选择。欧姆定律的另一个应用是限制供给特定设备的电流，可能用于降低触电风险，或保护设备本身。欧姆定律告诉我们，对于给定的电压，电阻越高，电流越低。因此，通过在设备上串联一个电阻，我们可以限制流经该设备的电流，从而防止可能的损坏。 您刚刚观看了 JoVE 关于欧姆定律的介绍视频。现在，您应该理解了电气元件两端的电压、其电阻以及通过它的电流之间的关系，以及电阻器、灯泡和发光二极管在电学行为上的差异。感谢观看！

Education

教育

JoVE Science Education

Physics

物理学

Physics II

物理 II

欧姆定律

measuring voltage, current, and resistance

This experiment measures voltage, current, and resistance in basic electric circuits. It also builds skill with circuit diagrams and the terms resistor, resistance, current, voltage, and power supply.

Students learn how to wire a circuit and how to measure current through a circuit component. They also measure the potential difference, or voltage, across a component. These steps help connect circuit symbols with real parts in the lab.

A power supply or battery provides voltage, measured in volts (V), that drives charge through the circuit. Circuit parts such as resistors and light bulbs limit how fast the charge flows. Current is measured in amperes (A), or amps, and resistance is measured in ohms (Ω).

The experiment also compares a basic resistor with a light bulb and a light-emitting diode, or LED. Light bulbs and LEDs appear in many common devices and lighting applications. Studying them helps explain how these parts work in everyday circuits.

Measuring Voltage, Current, and Resistance

electric fields

Visualizing Electric Field Lines

Electric field lines show how a charged object affects the space around it. A source charge creates an electric field, and that field can exert electric force on another charged object called the test charge. The electric field is a vector at each point in space, so it has both size and direction. The electric field is the electric force per unit test charge placed at a point. If a charge is placed in that field, the force on it equals the charge times the electric field. This makes electric...

electric potential

Voltage, Fields, and Equipotential Surfaces

Voltage, or electric potential, describes electric potential energy per unit charge. It is a scalar quantity, and it helps explain many electrical effects. In practice, the difference in electric potential is what matters most. Changes in electric potential across space are linked to the electric field. That field can produce an electric force on a charge. In a resistor, the difference in electric potential between two points drives electric current flow. This experiment uses a volt meter and...

magnetic fields

Magnetic Fields from Magnets and Currents

Magnetic fields come from moving electric charges and from magnetic materials such as bar magnets. A current is one example of moving charge. The magnetic field made by a current can be calculated with the Maxwell equation. Bar magnets also create magnetic fields. In magnetic materials, the field comes from tiny charge movements inside the material. These fields can be shown with small compass needle magnets, which turn to line up with the magnetic field. Magnetic fields push on other moving...

electric charge in a magnetic field

Measuring the Electron’s Charge-to-Mass Ratio

Measuring the electron’s charge-to-mass ratio is the focus of this physics experiment. It recreates J. J. Thomson’s famous experiment from the end of the 19th century. Thomson used it to measure the charge-to-mass ratio of the electron. This work also connects to Robert A. Millikan’s oil-drop experiment a few years later. Millikan’s result gave a value for the charge of the electron. Together, these experiments let scientists determine the electron’s mass and charge for the first time. Those...

investigation ohm's law for ohmic and nonohmic conductors

This experiment measures voltage, current, and resistance in basic electric circuits. It also builds skill with circuit diagrams and the terms resistor, resistance, current, voltage, and power supply. Students learn how to wire a circuit and how to measure current through a circuit component. They also measure the potential difference, or voltage, across a component. These steps help connect circuit symbols with real parts in the lab. A power supply or battery provides voltage, measured in...

series and parallel resistors

How Resistance Changes in Circuit Paths

Series and parallel resistor connections change how current and voltage behave in a circuit. This experiment shows how to find the total, or effective, resistance for each setup. It also uses Ohm’s law to relate voltage and current when the resistance is known. In a series circuit, resistors are wired one after the other. The same current flows through each resistor. Their voltages add together to make the total voltage, so the effective resistance is the sum of the individual resistances.

capacitance

Measuring Charge Storage in Capacitors

Capacitors store opposite charges on two conductors, such as two metal plates. This charge separation creates a potential difference, or voltage drop, between the conductors. In this experiment, commercial capacitors and a parallel plate capacitor are used to show how capacitance links charge and voltage. Capacitance is the proportionality factor between the amount of charge on each conductor and the voltage drop across it. When the voltage changes with time, the current flowing into the...

inductance

Magnetic Induction in Coils

Magnetic induction in coils is demonstrated with inductive coils and a voltmeter. A rod magnet is inserted into or pulled away from the core of a coil to create a brief electromotive force, or emf, in the coil. The voltmeter measures the resulting voltage change. The experiment also shows mutual inductance between two coils. When current in one coil is turned on or off, it can induce an emf in a nearby second coil. This makes the link between changing current and a voltage response clear. <br...

rc/rl/lc circuits

How RC, RL, and LC Circuits Change Over Time

RC, RL, and LC circuits show how current and voltage can change over time. These circuits combine resistors, capacitors, and inductors, which each behave differently in an electric circuit. A resistor dissipates energy and follows Ohm’s law, so its voltage is proportional to its current. A capacitor stores electrical energy. In a capacitor, current depends on how fast the voltage changes. An inductor stores magnetic energy. In an inductor, voltage depends on how fast the current changes. When...

semiconductors

Doping Silicon for p- and n-Types

Semiconductors conduct electricity in ways that depend on temperature and impurity level. Crystalline silicon is the most common semiconductor material. Pure semiconductors are usually not strong conductors, so they are often combined with a small amount of impurity to improve conductivity. This process is called doping. Donor impurities, such as phosphorus and arsenic, add electrons to silicon. Acceptor impurities, such as boron and aluminum, remove electrons from silicon. When acceptors take...

photoelectric effect

UV Light and Electron Emission

Photoelectric effect is the emission of electrons from a metal when light shines on it. The key idea is that the light must have a high enough frequency for its photons to carry enough energy. That energy increases with light frequency. This experiment shows the photoelectric effect with a charged zinc metal plate. The zinc is connected to an electroscope, which is an instrument that shows the presence and relative amount of charge. The plate is then exposed to either a regular lamp or...

reflection and refraction

Bending Light in Lenses and Materials

Light changes speed when it moves through different materials. When it crosses from one material to another, it may slow down or speed up. That change in speed makes the light bend. This bending is called refraction. Some of the light is also reflected at the boundary between the two materials. In special cases, the light can bend so sharply that it is completely reflected back into the material it came from. The lab explores the basic law of refraction and shows how this behavior affects...

interference and diffraction

Laser Slits Reveal Wave Patterns

Laser light can reveal wave behavior through interference and diffraction. These are common wave effects seen in many settings, from water waves to electromagnetic waves such as light. Interference happens when two waves of the same kind overlap. Their combined wave creates a repeating pattern of larger and smaller amplitude. Diffraction happens when a wave passes through an opening or moves around an object. In that case, different parts of the wave can interfere and produce a similar pattern...

standing waves

Standing Waves on a Slinky

Standing waves on a slinky show how wave superposition and reflection can create stable patterns. These waves, also called stationary waves, appear to stay in place even though the material is moving up and down. They are formed when two waves travel in opposite directions with the same frequency and amplitude. Standing waves are easy to spot in finite media. A plucked guitar string is a common example. Water in a lake and air in a room can also show this behavior. On a string fixed at both...

sound waves and doppler shift

Measuring Sound Speed with Motion

Sound waves and motion are the focus of this high school physics experiment. The lesson connects how sound travels through air with how the sound changes when the source moves. It also shows how to measure the speed of sound in air. Waves are disturbances that move through a material medium or through empty space. Light waves can travel through a vacuum and through some forms of matter. They are transverse waves, which means the oscillations are perpendicular to the direction of travel. Sound...

physics ii

本集探讨的主题包括静电、磁性、光学、波振荡和电路;解释那些改变了我们世界的物理现象背后的基本原则。

Measure voltage, current, and resistance in basic circuits while learning circuit diagrams, wiring, and how resistors, light bulbs, and LEDs behave.

Measuring Voltage, Current, and Resistance | JoVE K12

Andrew Duffy

Overview

Principles of Ohm&#8217;s law

Investigating Ohm&#8217;s Law for Ohmic Resistors

Investigating Ohm&#8217;s Law for Nonohmic Resistors

Applications

Summary

Energy and Work

Source: Ketron Mitchell-Wynne, PhD,&#160;Asantha Cooray, PhD, Department of Physics &#38; Astronomy, School of Physical Sciences, University of ...

Power and Energy

Energy is the total work required to drive the current through the circuit.
A rise in voltage results in more work done, passing more current, resulting ...

Heat Flow and Specific Heat

Heat is a type of energy transfer that is caused by a temperature difference, and it can change the temperature of an object. Since heat is a form of ...

Mechanisms of Heat Transfer I

Just as interesting as the effects of heat transfer on a system are the methods by which the heat transfer occur. Whenever there is a temperature ...

Mechanisms of Heat Transfer II

In convection, thermal energy is carried by the large-scale flow of matter. Ocean currents and large-scale atmospheric circulation, which result from the ...

conduction-convection-and-radiation-problem-solving

Conduction, Convection and Radiation: Problem Solving

There are three methods by which heat transfer can take place: conduction, convection, and radiation. Each method has unique and interesting ...

testing-the-heat-transfer-efficiency-of-a-finned-tube-heat-exchanger

Testing the Heat Transfer Efficiency of a Finned-tube Heat Exchanger

Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
Heat exchangers transfer ...

using-tray-dryer-to-investigate-convective-conductive-heat

Using a Tray Dryer to Investigate Convective and Conductive Heat Transfer

Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
Dryers are utilized in ...

Transformers

A device that transforms voltages from one value to another using induction is called a transformer. A transformer consists of two separate coils, or ...

conservation-of-energy-approach-to-system-analysis

Conservation of Energy Approach to System Analysis

Source: Ricardo Mejia-Alvarez and Hussam Hikmat Jabbar, Department of Mechanical Engineering, Michigan State University, East Lansing, MI
The purpose of ...

Dye-sensitized Solar Cells

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University
Today&#39;s modern world requires the use of a large amount of energy. While ...

Batteries and Fuel Cells

A battery is a galvanic cell that is used as a source of electrical power for specific applications. Modern batteries exist in a multitude of forms to ...

Design, evaluate, and refine a device that works within given constraints to transfer energy within a system.

HS+Phy.P4U2.7

What is Energy?

The universe is composed of matter in different forms, and all forms of matter contain energy. &#xA0;The different forms of energy on Earth originate from ...

Thermodynamic Systems

A thermodynamic system is a set of objects whose thermodynamic properties are of interest. The system is considered to be embedded in its surroundings or ...

Work

Work is done when energy is transferred from one object to another. In other words, work is when a force acts on something that undergoes a displacement ...

Kinetic Energy - I

It&#8217;s plausible to suppose that the greater the velocity of a body, the greater effect it could have on other bodies. This does not depend on the ...

Gravitational Potential Energy

Potential energy is not just a property of each object, but also a property of the interactions between objects in a chosen system. For each type of ...

Elastic Potential Energy

Elastic potential energy is the energy stored as a result of the deformation of an elastic object, such as the stretching of a spring. An object is ...

Work-energy Theorem

According to Newton&#x2019;s second law of motion, the sum of all the forces acting on a particle (net force) determines the rate of change in the ...

Power

The concept of work involves force and displacement; meanwhile, the work-energy theorem relates the net work done on a body to the difference in its ...

Phase Changes

Phase transitions play an important theoretical and practical role in the study of heat flow. In melting or fusion, a solid turns into a liquid; the ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Calorimetry

When objects at different temperatures are placed in contact with each other but isolated from everything else, they attain thermal equilibrium. A ...

Constant Volume Calorimetry

Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant ...

Constant Pressure Calorimetry

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a ...

Internal Energy

The internal energy of a thermodynamic system is the sum of the kinetic and potential energies of all the molecules or entities in the system. The kinetic ...

Enthalpy

Chemists ordinarily use a property known as enthalpy (H) to describe the thermodynamics of chemical and physical processes. Enthalpy is defined as the sum ...

First Law of Thermodynamics

A change in the internal energy of a system depends on the the net heat transfer into the system and the net work done by the system. The first law of ...

first-law-of-thermodynamics-problem-solving

First Law Of Thermodynamics: Problem-Solving

The first law of thermodynamics states that the change in internal energy of the system is equal to the net heat transfer into the system minus the net ...

using-differential-scanning-calorimetry-to-measure-changes-in-enthalpy

Using Differential Scanning Calorimetry to Measure Changes in Enthalpy

Source: Laboratory of Dr. Terry Tritt &#8212; Clemson University
Differential Scanning Calorimetry (DSC) is a method of thermodynamic analysis based on ...

Analyze and interpret data to quantitatively describe changes in energy within a system and/or energy flows in and out of a system.

HS+Phy.P4U1.6

Gel Purification

Gel purification is used to recover DNA fragments after electrophoretic separation. DNA recovery from an agarose gel includes three basic steps: binding, ...

Voltage

The movement of electrons in a conductor requires some form of energy or work, usually provided by an external force, like a battery. This force is called ...

Electrical Current

Electrical current is defined as the rate at which charge flows. When there is a large current present, such as that used to run a refrigerator, a large ...

Ohm's Law

Many materials exhibit a simple relationship between the values of current, voltage, and resistance, known as Ohm&#8217;s law. The current that flows ...

Resistance

When a current moves through any conductor, the conductor causes some level of difficulty for the current to flow. The measure of that difficulty is known ...

Electrical Power

Electric power is the product of current and voltage, represented in units of joules per second, or watts. For example, cars often have one or more ...

Energy Transfer in Chemical Reactions

Chemical reactions require sufficient energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ...

power-dissipated-in-a-circuit-problem-solving

Power Dissipated in a Circuit: Problem Solving

The equivalent resistance of a combination of resistors depends on their values and how they are connected.
The simplest combinations of resistors are ...

Kirchhoff's Current Law

Kirchhoff&#39;s current law, or KCL, is based on the law of charge conservation. It states that the total current entering and leaving a node in a circuit ...

Kirchhoff's Voltage Law

Kirchhoff&#39;s voltage law, or KVL, is based on the principle of energy conservation.
It states that the algebraic sum of all voltages around a closed ...

Resistors In Series

A resistor is an ohmic device that limits the flow of charge in a circuit. Most circuits have more than one resistor. If several resistors are connected ...

Resistors In Parallel

Resistors are in parallel when one end of all the resistors are connected to a continuous wire of negligible resistance and the other end of all the ...

Combination Of Resistors

Electrical devices in any circuit can be connected either by series or parallel connections. Additionally, circuits can be connected involving both of ...

Equivalent Resistance

In circuit analysis, situations often arise where resistors are neither in series nor parallel configurations. To tackle such scenarios, three-terminal ...

Source: Andrew Duffy, PhD, Department of Physics, Boston University, Boston, MA
This experiment investigates Ohm's law, which relates current, voltage, ...

Use mathematics and computational thinking to explain the relationships between power, current, voltage, and resistance.

Measuring Voltage, Current, and Resistance

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