Question

Bulbs A, B, and C in FIGURE Q28.10 are identical, and all are glowing.

a. Rank in order, from most to least, the brightnesses of the three bulbs. Explain.

b. Suppose a wire is connected between points 1 and 2. What happens to each bulb? Does it get brighter, stay the same, get dimmer, or go out? Explain

Short answer

a. $\mathit{A}\mathbf{>}\mathit{B}\mathbf{=}\mathit{C}$

b. Bulb A gets brighter in this example, whereas bulbs B and C go out.

Step-by-step solution

Given information and formula used 

Given :

Theory used :

a. The resistors in series have the same current.

b. The current through the resistor determines how much power passes through it

Ranking in order the brightnesses of the bulbs

(a) The resistors in series have the same current.

As a result, the current flowing through bulb A is the same as the current flowing through the two bulbs B and C combined. Because the current is greater, the brightness of bulb A is greater than that of C and B.

The current will be the same for both bulbs C and B because they are similar. As a result, C and B have the same brightness.

Hence, we rank the bulbs' brightness by $\mathit{A}\mathbf{>}\mathit{B}\mathbf{=}\mathit{C}$

Determining if the bulbs get brighter, stay the same, get dimmer, or go out 

(b) The current through the resistor determines how much power passes through it. When a wire is connected between points 1 and 2, current flows through this wire rather than bulb B or C.

As a result, there is no current flowing through bulbs B and C.

Bulb A gets brighter in this example, whereas bulbs B and C go out.