27.7
DC Battery
A conductor needs to be a component of a path that creates a closed loop or full circuit to have a continuous current flowing through it. A current st…
Two beakers with different levels of water are connected using a pipe. The potential difference makes the water flow until the levels become the same.
A water pump is required to maintain the potential difference for a continuous water flow.
Similarly, if an electric field is applied to an isolated conductor, current starts to flow. Hence, a net positive and negative charge accumulates at opposite ends.
They produce an equal and opposite electric field, making the total electric field zero, thus stopping the current.
To maintain a steady current in a circuit, it should be supplied with a device called a battery, which acts like a pump.
Inside a battery, because of the electrostatic field, an electron experiences a force. The battery's chemical energy provides a non-electrostatic force, which pushes it from the positive to negative terminal against the electrostatic force. This force maintains the potential difference between the terminals, converting chemical energy into electrical energy.
After reaching the negative terminal, the electrons move toward the positive terminal to complete the circuit.
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Q1: Why does current stop flowing in an isolated conductor without a battery?
When an electric field is applied to an isolated conductor, current initially flows. However, positive and negative charges accumulate at opposite ends, creating an equal and opposite electric field that cancels the applied field. This stops current flow because the total electric field becomes zero. A closed circuit with a battery is required to maintain continuous current.
Q2: How does a battery maintain a steady current in a circuit?
A battery acts like a pump, using chemical energy to provide a non-electrostatic force that pushes electrons from the positive to the negative terminal against the electrostatic force. This force maintains the potential difference between terminals, converting chemical energy into electrical energy and enabling continuous current flow through a closed circuit.
Q3: What is the relationship between potential difference and water flow in a circuit analogy?
Two beakers with different water levels connected by a pipe demonstrate potential difference. Water flows from high to low level until levels equalize. Similarly, in circuits, potential difference drives charge flow. A water pump maintains the difference for continuous flow, just as a battery maintains electrical potential difference for steady current.
Q4: Why must a complete circuit exist for continuous charge flow?
Charges lose potential energy passing through conductors. For charges to continue flowing from higher to lower potential, an external agent must return them from lower to higher potential, completing the loop. An open circuit cannot maintain consistent charge flow because charges cannot return to their starting point and potential energy cannot be restored.
Q5: How does a battery convert energy into electrical potential?
A battery converts chemical energy into electrical potential energy through internal non-electrostatic forces. These forces push electrons uphill against the electrostatic field, doing work per unit charge. This work, called electromotive force, transfers energy into the circuit, enabling current to flow from lower to higher potential within the battery.
Q6: What types of devices can serve as electromotive force sources?
Electromotive force sources include batteries, electric generators, solar cells, thermocouples, and fuel cells. All these devices convert energy from various sources—mechanical, chemical, thermal, or other forms—into electric potential energy that transfers into circuits to drive continuous current flow through the system.
Q7: What happens to electrons after they reach the negative terminal of a battery?
After reaching the negative terminal, electrons move toward the positive terminal through the external circuit to complete the closed loop. This continuous movement, driven by the battery's maintained potential difference, constitutes the steady current flowing through the circuit and returning to the battery's positive terminal.