物理電路 DSE、CE 選擇題（第 10 頁）

91.

6 V battery with R1 in series with R2 and R3 in parallel

In the circuit shown, the resistances of $R_1$ , $R_2$ and $R_3$ are all equal to $2\ \Omega$ . The power dissipated by $R_2$ is

92.

When connected in series in an electric circuit, the power dissipated in two resistors $R_1$ and $R_2$ is in the ratio of $1:4$ . What will be the ratio of the power dissipated in $R_1$ and $R_2$ when they are connected in parallel ?

93.

Junction with 3 A and 2 A entering, 1 A leaving, and an ammeter A in the remaining wire

In the circuit shown, what is the current passing through the ammeter $A$ ?

94.

Circuit with ammeters A1, A2 and A3, two resistors, a battery and a switch S

In the above circuit, $A_1$ , $A_2$ and $A_3$ are ammeters of negligible internal resistance. What will happen to the readings of the ammeters if the switch $S$ is closed ?

Reading of $A_1$	Reading of $A_2$	Reading of $A_3$
decreases	increases	becomes zero
increases	decreases	becomes zero
unchanged	increases	becomes zero
unchanged	decreases	increases

95.

The resistance of a given conducting wire may be increased by

(1)decreasing the radius of the wire.

(2)increasing the length of the wire.

(3)winding the wire in the form of a coil.

96.

Which of the following are vectors ?

(1)weight

(2)charge

(3)voltage

97.

Lamp L1 in the top branch, lamps L2 and L3 in a middle branch, cell in the bottom branch

In the circuit shown, the cell has negligible internal resistance. If the lamp $L_3$ burns out, then

98.

Suppose you were given four similar lamps and a battery. Which of the following ways of connecting the lamps to the battery would give the maximum brightness overall ?

Four circuits A to D, each connecting four lamps to a battery in different series/parallel arrangements

99.

In the circuit shown, the cell has negligible internal resistance. The two resistors $R$ are identical. If the power dissipated in the circuit is $P$ when $K$ is open, find the power dissipated when $K$ is closed.

Cell in series with a resistor R, then a second resistor R in parallel with a switch K

100.

Battery with three resistors and a voltmeter connected across one resistor

In the given circuit diagram, the battery has a voltage of $6$ V and negligible internal resistance. The three resistors are identical and the voltmeter has the same resistance as each resistor. What is the reading on the voltmeter ?