Question

The potential difference between the terminals of an electric heater is 60v whenit draws a current of 4a from the source. What current will the heater draw if the potential difference is increased to 120v?

Answer 1

Using V=IR in first case
60=4r (r=resistance)
r=15
Since the resistance remains constant; using V=IR in second case
120=15i (I=current)
i=8a
Hence it will draw a current of 8a.

Answer 2

Answer:

The current through the heater becomes 8 A.

Explanation:

Given,

The potential difference between the terminals of an electric heater is 60 V.

Current of 4 A is drawn from the source.

To find: What current will the heater draw if the potential difference is increased to 120 V

Solution:

According to Ohm's law, Potential difference is directly proportional to current.

i.e V  $\propto$  I

or, V = iR

here, V = 60 V and i = 4 A

Substituting the values,

R = V / i = 60 / 4 = 15 Ω

Now, V is increased to 120 V.

Again using ohm's law,

i = V / R = 120 / 15 =  8 A

Therefore, The current through the heater becomes 8 A.