Question

An electrical appliance draws 4 A from a 230 V supply line. When the same appliance is connected to 110 V, the amount of current drawn is _________.
1. 1.8 A
2. 1.5 A
3. 1.6 A
4. 1.91 A

Answer 1

Correct Answer - Option 4 : 1.91 A

CONCEPT:

Ohm's law

Ohm’s law states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperature remain constant.

​\(\Rightarrow V=IR\)

Where V = voltage, I = current and R = resistance

CALCULATION:

Given V1 = 230 V, I1 = 4 A and V2 = 110 V

According to ohm's law,

\(\Rightarrow V=IR\)     -----(1)

By equation 1 for V1 = 230 V,

\(\Rightarrow V_{1}=I_{1}R\)

\(\Rightarrow R=\frac{V_{1}}{I_{1}}\)

\(\Rightarrow R=\frac{230}{4}\,\Omega\)     -----(2)

By equation 1 for V2 = 110 V,

\(\Rightarrow V_{2}=I_{2}R\)

\(\Rightarrow I_{2}=\frac{V_{2}}{R}\)

\(\Rightarrow I_{2}=\frac{110\times4}{230}\)

\(\Rightarrow I_{2}=1.91A\)

Hence, option 4 is correct.