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Chapter 19: Q23Q (page 796)

A desk lamp that plugs into a wall socket can use a or a light bulb. Which bulb has the larger resistance? Explain briefly.

Short Answer

Expert verified

The bulb has the larger resistance.

Step by step solution

01

Given data

Input voltage:

V=120V

Output power of first bulb:

P1=60W

Output power of second bulb:

P2=100W

02

Resistance of a bulb

The resistance of a bulb of wattage when connected to an input voltage is

R=V2P

03

Determination of resistances of the two bulbs

From the above equation, the resistance of the first bulb is:

R1=V2P1=120V260W=240.1V2/W×1Ω1V2/W=240Ω

From the above equation, the resistance of the second bulb is:

R2=V2P2=120V2100W=144.1V2/W×1Ω1V2/W=144Ω

Thus, the first bulb has the larger resistance.

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Most popular questions from this chapter

(a) If the current through a battery is doubled, by what factor is the battery power increased? (b) If the current through a resistor is doubled, by what factor is the power dissipation increased? (c) Explain why these factors are the same or different (depending on what you find).

A battery with negligible internal resistance is connected to a resistor. The power produced in the battery and power dissipated in the resistor are both P1. Another resistor of same kind is added, so circuit consists of a battery and two resistors in series. (a) in terms of P1 how much power is dissipated in the first resistor ? . (a) in terms of P1 how much power is produced in the battery ? (c ) The circuit is rearranged so that the two resistors are in parallel rather than in series. In terms of P1, now how much power is produced in the battery?

You connect a 9 Vbattery to a capacitor consisting of two circular plates of radius 0.08 mseparated by an air gap of 2mm, what is the charge on the positive plate?

Suppose that instead of placing an insulating layer between the plates of the capacitor shown in Figure 19.57, you inserted a metal slab of the same thickness, just barely not touching the plates. In the same circuit, would this capacitor keep the current more nearly constant or less so than capacitor 2 in Question Q4? Explain why this is essentially equivalent to making a capacitor with a shorter distance between the plates.

For the circuit shown in figure 19.86, which consists of batteries with known emf and ohmic resistors with known resistance, write the correct number of energy-conservation and current node rule equations that would be adequate to solve for the unknown currents, but do not solve the equations. Label nodes and currents on the diagram, and identify each equation (energy or current, and for which loop or node).
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