Electrical circuits：練習問題

What is the SI unit for potential difference?

A battery is connected to two resistors, \(R_1\) and \(R_2\), in a parallel circuit. The resistance of \(R_1\) is \(12 \, \Omega\) and the resistance of \(R_2\) is \(6 \, \Omega\). If an ammeter in the main loop measures a total current of \(1.5 \, \text{A}\), what is the current flowing through resistor \(R_2\)?

In a simple series circuit containing two identical light bulbs and a battery, what happens to the remaining light bulb if one of the light bulbs burns out and creates an open circuit?

In a simple electrical circuit, what is the standard SI unit for electric current and which instrument must be connected in series to measure it?

A student investigates how the thickness of a metal wire affects its resistance. If wire A and wire B are made of the same material and have the same length, but wire B has a larger cross-sectional area, which of the following is true?

How does the electrical resistance of a uniform metal wire change if its length is increased?

Describe the key difference in how electric current behaves (flows) through components connected in a series circuit compared to components connected in a parallel circuit.

A circuit consists of a 12 V battery connected to a series combination of two resistors, $$R_1 = 2 \, \Omega$$ and $$R_2 = 4 \, \Omega$$. In parallel with $$R_2$$, there is a third resistor $$R_3 = 6 \, \Omega$$. If the internal resistance of the battery is $$0.5 \, \Omega$$, calculate the total power dissipated by the external circuit (i.e., by $$R_1$$, $$R_2$$, and $$R_3$$).

For an electrical appliance to work, it must be part of a complete and functional circuit.

(a) In a basic circuit, which component serves as the primary energy source required to make a bulb light up?

(b) Briefly explain the difference between an electrical conductor and an electrical insulator.

(c) Give one example of a material that is a good electrical conductor.

You are given a 9 V battery, a switch, an ammeter, and two identical light bulbs (L1 and L2).

(a) Draw a labelled circuit diagram to show how these components should be connected so that:
(i) Both L1 and L2 light up when the switch is closed.
(ii) If L1 breaks, L2 also goes out.
Include the ammeter in your diagram to measure the total current from the battery. Use standard circuit symbols.

(b) Explain why L2 goes out if L1 breaks in the circuit you designed in (a).

(c) Now, draw a second labelled circuit diagram using the same components (9V battery, switch, ammeter, L1, L2) such that:
(i) Both L1 and L2 light up when the switch is closed.
(ii) If L1 breaks, L2 remains lit.
Place the ammeter to measure the current flowing through L1. Use standard circuit symbols.

(d) Compare the total resistance of the circuit in (a) with the total resistance of the circuit in (c). Which one is likely higher? Justify your answer.