物理電路 DSE、CE 選擇題（第 3 頁）

21.

Label: Lithium cell 3.6 V, Capacity 800 mA h, Time (stand-by mode) about 3 days

The figure shows a label on a lithium cell of a mobile phone. The capacity $800$ mA h indicates the quantity of electric charges that the cell will discharge in $3$ days when the mobile phone is in stand-by mode. Estimate the average power of the cell assuming the voltage remains constant during the discharge.

22.

Battery with three parallel branches: one bulb with ammeter A2, two bulbs in series with ammeter A1, and ammeter A3 in the main line

In the above circuit, the bulbs are identical. If the reading of $A_1$ is $1$ A, find the readings of ammeters $A_2$ and $A_3$ .

	Reading of $A_2$	Reading of $A_3$
	$0.5$ A	$1$ A
	$0.5$ A	$1.5$ A
	$2$ A	$2$ A
	$2$ A	$3$ A

23.

12 V battery with resistors R1 and R2 and switch S in series, voltmeter across R2 and the switch

In the above circuit, what is the reading of the voltmeter when switch $S$ is closed ?

24.

Pictorial circuit with battery box, switch, ammeter, voltmeter, rheostat and resistor R

A student wants to measure the resistance of a resistor $R$ and sets up a circuit as shown above. Which of the following describe(s) the mistake(s) made by the student in setting up the circuit ?

(1)The polarity of the ammeter is reversed.

(2)The polarity of the voltmeter is reversed.

(3)The voltmeter is connected across both

R

and the rheostat.

25.

Questions 84 and 85 :

Circuit with cell, ammeter, resistor and thermistor in series and a voltmeter across the thermistor

A teacher sets up the circuit as shown in the above Figure and provides the following information to her students.

Information scroll: thermistors are devices whose resistance varies with temperature; graph of resistance against temperature falling steeply then flattening

Which of the following shows the variation of the ammeter reading $I$ with the temperature of the thermistor $\theta$ ?

26.

Questions 84 and 85 :

A teacher sets up the circuit as shown in the above Figure and provides the following information to her students.

Which of the following shows the variation of the voltmeter reading $V$ with the temperature of the thermistor $\theta$ ?

27.

Rechargeable cell labelled Standard charge 16 hours at 190 mA, Fast charge 5 hours at 475 mA

The photograph shows a rechargeable cell. If the cell is charged for $16$ hours using the standard charge mode, estimate the total amount of charge flowed through the charging circuit.

28.

An ammeter with negligible resistance and a high-resistance voltmeter are connected into a circuit as shown. Find the ammeter and voltmeter readings.

6 V battery with three 2 ohm resistors in series, a voltmeter across the first and an ammeter across the last two

	Ammeter reading / A	Voltmeter reading / V
	$0$	$2$
	$1$	$2$
	$3$	$2$
	$3$	$6$

29.

6 V battery, ammeter and rheostat with sliding contact X on AB

An ammeter and a rheostat of range $0-40\ \Omega$ are connected to a $6$ V battery. The sliding contact is located at a position $X$ where $AX=\frac{1}{4}AB$ as shown above. Find the ammeter reading.

30.

6 V battery with resistor X; 12 V battery with resistors Y and Z in parallel

In the above circuits, $X$ , $Y$ and $Z$ are identical resistors. The power dissipated in $X$ is $20$ W. Find the total power dissipated in $Y$ and $Z$ .