Question

You are given three bulbs of 25, 40 and 60 watts. Which of them has lowest resistance ?

• A. 25 watts
• B. 40 watts
• C. 60 watts
• D. None of the above

Answer 1

Answer:

C. 60 watts

• The power consumed by an electrical appliance like a bulb is related to the voltage across it and the current flowing through it. The fundamental formula is P = V * I, where P is power, V is voltage, and I is current.

• Using Ohm's Law (V = I * R), we can derive other useful relationships.

• When voltage (V) is constant (as is typically the case for household bulbs connected to the same mains supply), the power dissipated by a resistor is given by: P = V^2 / R.

• Rearranging this formula to find resistance, we get: R = V^2 / P.

• We are given three bulbs with power ratings of 25 W, 40 W, and 60 W.

• Since all bulbs are assumed to be connected to the same voltage source (e.g., household electricity), the voltage (V) is constant for all of them.

• From the formula R = V^2 / P, we can see that resistance (R) is inversely proportional to power (P) when voltage is constant. This means that a higher power rating will correspond to a lower resistance.