物理家居用電 DSE、CE 選擇題（第 2 頁）

11.

Kilowatt-hour meter label: 220 V, 50 Hz, circular disc, 600 revolutions / kWh

The figure shows the label of a kilowatt-hour meter connected to a mains supply. When an appliance is switched on for $2$ minutes, the circular disc rotates through $24$ complete revolutions. What is the electric power consumed by the appliance ?

12.

An electric appliance draws a current $2$ A when it is operating at $220$ V. Which of the following is the best description of the current and the voltage of each wire of the electric appliance when it is connected to a $220$ V mains supply ?

Live wire: Current	Live wire: Voltage	Neutral wire: Current	Neutral wire: Voltage	Earth wire: Current	Earth wire: Voltage
$2$ A	$220$ V	$1$ A	$220$ V	$1$ A	$0$
$2$ A	$220$ V	$2$ A	$220$ V	$0$	$0$
$2$ A	$220$ V	$2$ A	$0$	$0$	$0$
$2$ A	$220$ V	$0$	$0$	$0$	$0$

13.

Two light bulbs are marked ' $220$ V, $50$ W' and ' $220$ V, $100$ W' respectively. If they are connected in series to a $220$ V mains supply, what is the current drawn from the mains supply ?

14.

In the circuit shown, the resistors represent the heating elements in a rice cooker. The resistances of the elements are $5R$ and $R$ respectively. The rice-cooker can be operated in two modes, namely, cooking and keeping warm. The power consumed by the cooker in the cooking mode is $600$ W when $S$ is closed. What is the power consumed by the rice-cooker in the mode of keeping warm when $S$ is open ?

Circuit with switch S in parallel with a 5R resistor, in series with a resistor R and the mains

15.

The following table shows three electrical appliances which Clara used in a certain month :

Appliance	Rating	Duration
air-conditioner	$220$ V, $1200$ W	$250$ hours
television	$220$ V, $250$ W	$80$ hours
computer	$220$ V, $150$ W	$60$ hours

Calculate the cost of electricity used. Note : $1$ kW h of electricity costs $\$0.86$ .

16.

If a $15$ A fuse is installed in the plug of an electric kettle of rating value ' $220$ V, $900$ W', which of the following descriptions is correct ?

17.

One day, Donald used the following electrical appliances at home :

Appliance	Rating	Duration	Cost of electricity
electric heater	$220$ V, $2500$ W	$30$ minutes	$C_1$
television	$220$ V, $270$ W	$5$ hours	$C_2$
lamp	$220$ V, $150$ W	$8$ hours	$C_3$

Which of the following relationships is correct ?

18.

12 V battery connected in parallel to bulbs P, Q and R

Three light bulbs $P$ , $Q$ and $R$ of ratings ' $24$ V, $80$ W', ' $12$ V, $80$ W' and ' $12$ V, $40$ W' are connected in parallel to a $12$ V battery. Which of the bulbs will be the brightest, and which will be the dimmest ?

	The brightest	The dimmest
	$P$	$Q$
	$P$	$R$
	$Q$	$P$
	$Q$	$R$

19.

Photograph of a three-pin plug with pin P indicated

The photograph shows a three-pin plug of an appliance. Which of the following is a function of pin $P$ ?

20.

Energy label of a washing machine showing annual energy consumption 250 kWh/year

The figure shows the energy label of a washing machine. If the average working time per wash is $1.8$ hours, estimate the average electric power consumed by the machine.