Question

the potential difference b/w the terminals of an electric heater is 60V when it draws a current of 4A from the source. What will the heater draw if the potential difference is increased to 120V ?

Answer 1

we have to remember the fact that for a given material the resistance is constant. so the resistance is same throughout

We know the equation V= I*R
    where, 
            V= potential difference 
          I= current
           R= resistance 

it is given that V= 60 V
                       I= 4A
    
 applying the equation, R= V/I
                                     R= 60 /4
                                     R= 15Ω

in next condition,  
 V= 120 V
    
 I= V/R
I= 120 / 15
I= 8 A

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.