Electricity：練習題

Which of the following is a potential hazard associated with using an electrical appliance in damp conditions or with damaged insulation?

In a simple series circuit, three different resistors are connected to a cell. An ammeter is placed between the first and second resistor. If the ammeter reading is \( 0.45 \, \text{A} \), what is the current flowing through the third resistor?

A \( 12.0 \, \text{V} \) battery is connected in series with two resistors of \( 4.0 \, \Omega \) and \( 8.0 \, \Omega \). A voltmeter is connected across the \( 8.0 \, \Omega \) resistor. What is the reading on the voltmeter?

A plastic rod is rubbed with a woollen cloth, and the rod becomes negatively charged.

Which statement correctly explains why the rod becomes negatively charged?

A student connects two resistors, each with a resistance of \( 10 \, \Omega \), in parallel to a battery.

What can be concluded about the total combined resistance of this arrangement?

A simple circuit consists of a battery and a lamp. The battery moves a total charge of \( 120 \text{ C} \) around the circuit, transferring \( 720 \text{ J} \) of energy.

Calculate the electromotive force (e.m.f.) of the battery.

A filament lamp is labelled 12 V and 24 W. Calculate the current passing through the lamp when it is operating normally at its rated voltage.

A uniform metal wire has a resistance of \( 6.0 \, \Omega \). A second wire of the same material is twice as long and has half the cross-sectional area of the first wire. Determine the resistance of this second wire.

A simple series circuit consists of a 9.0 V battery connected to a switch and two identical fixed resistors.

(a) The switch is closed, and an ammeter in the circuit shows a reading of 0.6 A. Determine the total resistance of the circuit. [2]

(b) Calculate the resistance of a single resistor in this circuit. [1]

(c) State what happens to the total current in the circuit if a third identical resistor is added in series with the other two. Explain your answer. [2]

In the circuit diagram described, a battery with an electromotive force (e.m.f.) of \( 12.0 \, \text{V} \) is connected in series with two fixed resistors. Resistor \( R_1 \) has a resistance of \( 10.0 \, \Omega \) and resistor \( R_2 \) has a resistance of \( 20.0 \, \Omega \).

(a) Calculate the total resistance of the circuit.
(b) Determine the reading on an ammeter placed in the main circuit.
(c) Calculate the potential difference across resistor \( R_2 \).