Chapter 19, Problem 4Q

To determine

       • Which bulb is brighter when connected in series?

       • Which bulb is brighter when connected in parallel?

Answer to Problem 4Q

Solution:

       • In series connection, the bulb with highest resistance will be the brighter.

       • In parallel connection, the bulb with lowest resistance will be the brighter.

Explanation of Solution

In series connection, the current is same and the power in the circuit is given by the formula.

        $P=I^{2}R$

It is clear from the above expression that power is directly proportional to resistance if current in the circuit is constant; therefore, the bulb with higher resistance will be brighter.

In parallel connection the voltage is same, and the power in the circuit is given by the formula.

        $P=\frac{V^2}{R}$

It is clear from the above expression that power is inversely proportional to resistance, if voltage in the circuit is constant; therefore, the bulb with lower resistance will be the brighter.