Correct Answer - Option 1 : the supply voltage has dropped and the current reduced, but not the resistance.
CONCEPT:
-
Resistance: The measure of the opposition to current flow in an electrical circuit is called its resistance.
- The resistance of a wire depends on its length, area, and metal resistivity.
Resistance is calculated by:
\(R=\rho{l \over A}\)
where l is its length, A area, and ρ is its metal resistivity, σ is conductivity.
-
Ohm's Law: A law that states that electric current is proportional to voltage and inversely proportional to resistance.
Mathematically,
V = IR or I = V/R
where R is the resistance, I is current, and V is the voltage across the conductor.
Power in resistance:
\(P=VI = {V^2\over R}=I^2R\)
where V is the voltage and I is the current.
EXPLANATION:
- Since the resistance depends on its length, area, and metal resistivity, and the bulb, it will not change.
- So the resistance of the bulb will not change.
- The bulb will dimmer If the power of the bulb decreases.
-
The power of the bulb P = VI will decrease if voltage or current decreases.
- So Light suddenly becoming dimmer may mean very likely the supply voltage has dropped and the current reduced, but not the resistance.
- So the correct answer is option 1.
