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Question

(a) Name a device which helps to maintain a potential difference across the ends of a conductor.

(b) What is meant by saying that the potential difference between two points is 1 V?

(c) Define Ohm's law. Write an expression for it.

(d) What is the unit of resistance?

ā(e) When the potential difference between the terminals of an electric heater is 110 V, a current of 5 A flows through it. What current will flow through the heater if the potential difference is increased to 220 V? What is the resistance of heater?

(b) What is meant by saying that the potential difference between two points is 1 V?

(c) Define Ohm's law. Write an expression for it.

(d) What is the unit of resistance?

ā(e) When the potential difference between the terminals of an electric heater is 110 V, a current of 5 A flows through it. What current will flow through the heater if the potential difference is increased to 220 V? What is the resistance of heater?

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Solution

(a) The potential difference across the ends of a conductor is maintained by connecting a battery or a dry cell at the ends of the conductor.

(b) When 1 Joule of work is done to move a 1 Coulomb charge from one point to another, then the potential difference between the two points is said to be 1 Volt (V).

(c) According to Ohm's Law, the current flowing in a circuit is directly proportional to the applied potential difference.

Mathematical expression for Ohm's Law: $V\propto I$ or V = IR (Where 'R' is the constant of proportionality and is known as the resistance of the circuit)

(d) Unit of resistance is Ohm, denoted by the symbol $\mathrm{\Omega}$.

(e) According to Ohm's law, V = IR

$\Rightarrow R=\frac{V}{I}=\frac{110\mathrm{V}}{5\mathrm{A}}=22\mathrm{\Omega}$

Hence, the resistance of the heater is $22\mathrm{\Omega}$.

Now, if the potential difference is changed to 220 V, then the current in the circuit = $I=\frac{V}{R}=\frac{220\mathrm{V}}{22\mathrm{\Omega}}=10\mathrm{A}$

(b) When 1 Joule of work is done to move a 1 Coulomb charge from one point to another, then the potential difference between the two points is said to be 1 Volt (V).

(c) According to Ohm's Law, the current flowing in a circuit is directly proportional to the applied potential difference.

Mathematical expression for Ohm's Law: $V\propto I$ or V = IR (Where 'R' is the constant of proportionality and is known as the resistance of the circuit)

(d) Unit of resistance is Ohm, denoted by the symbol $\mathrm{\Omega}$.

(e) According to Ohm's law, V = IR

$\Rightarrow R=\frac{V}{I}=\frac{110\mathrm{V}}{5\mathrm{A}}=22\mathrm{\Omega}$

Hence, the resistance of the heater is $22\mathrm{\Omega}$.

Now, if the potential difference is changed to 220 V, then the current in the circuit = $I=\frac{V}{R}=\frac{220\mathrm{V}}{22\mathrm{\Omega}}=10\mathrm{A}$

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