物理電路 DSE、CE 選擇題（第 5 頁）

41.

Battery with resistor R, ammeter A in series and a voltmeter V connected across R and the ammeter

A student uses the above circuit to find the resistance of a resistor $R$ (i.e. resistance $=\dfrac{\text{voltmeter reading}}{\text{ammeter reading}}$ ). Which of the following statements is/are correct ?

(1)The ammeter reading records the actual current passing through

R

.

(2)The voltmeter reading records the actual voltage across

R

.

(3)The value of the resistance of

R

obtained is smaller than its actual value.

42.

Cell delivering current I to three parallel resistors of 60 ohm, 60 ohm and 30 ohm

In the above circuit, the current delivered by the cell is $I$ . What is the current passing through the $30\ \Omega$ resistor ?

43.

6 V battery with resistor R in series with an ammeter and 6 ohm resistor in parallel with a 12 ohm resistor

In the above circuit, the reading of the ammeter is $0.4$ A. Find the resistance of the resistor $R$ .

44.

Which of the following expressions represents a physical quantity which is different from the others ?

45.

All the resistors in the below networks are identical.

Three resistor networks (1), (2) and (3)

Arrange the networks in ascending order of equivalent resistances :

46.

Battery with switch S, ammeter A, heater Y in series, and heater X with a voltmeter V across it

In the circuit shown, $X$ and $Y$ are identical heaters. The ammeter has negligible resistance while the voltmeter has very high resistance. When switch $S$ is closed, the ammeter records a reading but the voltmeter reading is zero. Which of the following provides a possible explanation ?

47.

Which of the following expressions does not represent energy ?

48.

Battery with 6 ohm resistor and ammeter A1 in series with 4 ohm resistor in parallel with 6 ohm resistor and ammeter A2

In the circuit shown, the reading of ammeter $A_2$ is $0.3$ A. Find the reading of ammeter $A_1$ .

49.

It is known that the resistance of a resistor $R$ is about $5\ \mathrm{k}\Omega$ . Which of the following circuits is most suitable for measuring the resistance of $R$ ? The ammeter and voltmeter used are common moving coil meters.

Four circuits A to D with a battery, resistor R, ammeter and voltmeter connected in different ways

50.

Figure (a): battery, ammeter and two resistors R in series. Figure (b): battery, ammeter and two resistors R in parallel

In Figure (a), the ammeter reading and the total power dissipated in the two identical resistors are $I$ and $P$ respectively. The resistors are rearranged as shown in Figure (b). Find the ammeter reading and the total power dissipated in the two resistors.

	Ammeter reading	Total power dissipated
	$2I$	$2P$
	$2I$	$4P$
	$4I$	$2P$
	$4I$	$4P$