Question 1

A bird can safely perch on a high-voltage power line, but a person touching a power line with a metal ladder is at great risk. Which of the following best explains this difference?

Accepted Answer

Birds are not grounded, so there is almost no potential difference across their bodies, resulting in negligible current.

Question 2

You have a 120-V power supply and several 6-V lamps. How can you connect the lamps so that each receives exactly 6 V without burning out?

Accepted Answer

Connect 20 lamps in series so that the voltage divides equally, giving each lamp 6 V.

Question 3

Two lightbulbs, one with resistance $$R_1$$ and one with resistance $$R_2$$ ($$R_2$$ \u003e $$R_1$$), are connected in series to a battery. Which bulb is brighter and why?

Accepted Answer

The bulb with $$R_2 is $$brighter because power in series is $$P = I^2$ R$$ and both have the same current.

Question 4

If you connect two identical resistors in series to a battery, compared to using only one resistor, what happens to the total power supplied by the battery?

Accepted Answer

The power decreases because the total resistance increases.

Question 5

Why are household electrical outlets wired in parallel rather than in series?

Accepted Answer

So that each outlet receives the same voltage and can operate independently.

Question 6

You have two identical lightbulbs and two identical batteries. How should you arrange them to maximize the total power delivered to the bulbs?

Accepted Answer

Connect the batteries in series and the bulbs in parallel.

Question 7

Suppose you add a 100-W bulb to a circuit already containing a single 60-W bulb, both connected to the same voltage source. What happens to the total resistance of the circuit?

Accepted Answer

The total resistance decreases.

Question 8

Three identical capacitors are connected to a battery. In which configuration do they store the most energy, and why?

Accepted Answer

In parallel, because the equivalent capacitance is maximized and $$PE = \frac{1}{2} C V^2$.

Question 9

Why is it more dangerous to operate an electric appliance while standing barefoot outside than while wearing shoes indoors?

Accepted Answer

Bare feet have lower resistance, allowing more current to flow through your body if there is a fault.

Question 10

What is the main difference in the internal construction of an analog ammeter versus an analog voltmeter?

Accepted Answer

An ammeter has a small shunt resistor in parallel with the galvanometer; a voltmeter has a large resistor in series with the galvanometer.

Question 11

If you mistakenly connect an ammeter across a voltage source (in parallel), what is the likely outcome?

Accepted Answer

The ammeter will be damaged due to excessive current.

Question 12

A voltmeter connected across a resistor always reads less than the actual voltage across the resistor (when the meter is not present). Why?

Accepted Answer

The voltmeter decreases the total resistance, reducing the voltage drop across the resistor.

Question 13

A flashlight bulb is dim, but when you check the battery with a voltmeter, it reads 1.5 V. What is the most likely explanation?

Accepted Answer

The battery's internal resistance is high, so under load the terminal voltage drops below the emf.

Question 14

When are batteries connected in series, and when are they connected in parallel? Why is it important that batteries are nearly identical when connected in parallel?

Accepted Answer

Series for higher voltage, parallel for longer battery life; non-identical batteries in parallel can cause one to charge the other.

Question 15

Can the terminal voltage of a battery ever exceed its emf? Under what condition?

Accepted Answer

Yes, when the battery is being charged and current is forced backward through it.

Question 16

Which of the following statements about resistors and capacitors in series and parallel is correct?

Accepted Answer

Resistors in series add directly; capacitors in parallel add directly.

Question 17

If a battery remains connected to a capacitor network while you rearrange the capacitors, what quantity remains constant?

Accepted Answer

The voltage across the network.

Question 18

Which configuration results in the highest total capacitance: three identical capacitors in series or in parallel?

Accepted Answer

Parallel, because the capacitances add directly.

Question 19

If you add more resistors in parallel to a circuit, what happens to the total current drawn from the voltage source?

Accepted Answer

The total current increases.

Question 20

Which equation correctly gives the power dissipated by a resistor when connected to a voltage $$V$$?

Accepted Answer

$$P = V^2$ / R$$

Conceptual Physics: Circuits, Resistance, Power, and Measurement

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