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**(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?

**(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?

**a)** A **cell **or a battery helps to maintain a potential difference across a conductor.

**b)**Potential difference is defined as the work done in moving one coulomb of charge from one point to the other.

Thus, the potential difference between the two points is said to be 1 volt if work done in transferring 1 coulomb of charge from one point to the other point is 1 joule.

c) Ohm's law states that the voltage across a resistor is directly proportional to the current flowing through it. Ohm's law is named for German physicist Georg Ohm.

Mathematically this relationship is given as,

V = I × R

where,

**V**= voltage across resistor

**I**= current

**R**= resistance

**d)**The standard unit of resistance is the

**ohm.**

**e) Given**,

Potential difference,

**V = 110V**Current,

**I = 5A**Increment of potential difference =

**220 V**

**To find:**Current flow through the heater if the potential difference is increased to 220 V and the resistance of heater

**(R)**.

**Solution:**

By ohm's law,

**$R=\frac{V}{I}$**

Substituting the given values in the above expression we get-

**$R=\frac{110}{5}=22\Omega $**

Now,

When the potential difference is increased to 220V, the current drawn by the heater will be:

$I=\frac{V}{R}$

Substituting the given values in the above expression.

$I=\frac{220}{22}=10A $

Thus the current drawn by the heater is doubled when the potential difference across the terminals get doubled.

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