The potential difference between an electric heater's terminals is 80 V when a current of 6 Ampere is drawn from the source. If the potential difference is adjusted to 135 V, how much current would the heater draw? 

According to Ohm's law, the potential difference across a current-carrying wire is directly proportional to the current flowing through it under constant temperature and the proportionality constant is nothing but the resistance offered by the circuit.

V = RI

Where V is the potential difference, R is the resistance and I is the current.

Therefore, Resistance R = $\frac{\mathrm{V}}{\mathrm{I}}$

V = 80 V, I = 6 A

$\Rightarrow$R = $\frac{80}{6}$= 13.33 Ohms

The resistance of the circuit remains constant.

$\therefore$In the second instance, V = 135 V, R =13.33 $\Omega$

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

$\therefore$I = $\frac{135}{13.33}$= 10.12 A

Therefore, when the potential difference is adjusted to 135 V, 10.12 A current will flow through the circuit.