Question

Three bulbs of 25W, 50W, and 100W are connected to a same voltage circuit, Which bulb has most resistance?
1. 25 W
2. 50 W
3. 100 W
4. All will have the same resistance

Answer 1

Correct Answer - Option 1 : 25 W

CONCEPT:

• Resistance: The measure of the opposition to current flow in an electrical circuit is called its resistance.

Power in resistance:

 \(P=VI = {V^2\over R}=I^2R\)

where V is the voltage and I is the current.

EXPLANATION:

• Since every appliance is connected in parallel to other appliances and voltage sources, all electrical appliances in a household circuit work at the same voltage.

We know the power of an electric appliance is given by

\(P={V^2\over R}\)

\(R={V^2\over P}\)

\(R\propto{1\over P}\)

• So The low-power devices will have more resistance.
• The Power of a 25-watt bulb is the least in the given bulbs.
• So, the 25 W bulb has the most resistance.
• Hence the correct answer is option 1.