物理 2003 年 DSE、CE 選擇題（第 4 頁）

31.

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 $P$ ?

32.

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.

33.

Which of the following statements about $\alpha$ particles and $\gamma$ rays is/are correct ?

(1)They can both be deflected by a magnetic field.

(2)

\alpha

particles have a stronger ionizing power than

\gamma

rays.

(3)They are emitted with almost the same speed in radioactive decay.

34.

Two decay graphs: activity of P falls from 800 Bq to 400 Bq at 10 min; activity of Q falls from 800 Bq to 200 Bq at 10 min

The figures above show the variation of the activities of two radioactive sources $P$ and $Q$ with time. Find the ratio of the half-life of $P$ to that of $Q$ .

35.

Which of the following are essential criteria in choosing radioactive sources as medical tracers in human bodies ?

(1)The sources should have a short half-life.

(2)The radiation emitted should have a weak ionizing power.

(3)The radiation emitted should not be deflected by an electric field.