1989 年

A stationary wave is formed in a string. The above diagram shows the string at the instant of maximum displacement. What will be the shape of the wave pattern one quarter of a period later ?

In the circuit shown, resistors $A$, $B$ and $C$ are identical. When $K$ is open, the power dissipated by $A$ is $P_1$. When $K$ is closed, the power dissipated by $A$ becomes $P_2$. The ratio $P_1:P_2$ is equal to

In the circuit shown, a $4\ \Omega$ resistor is to be connected to two of the terminals $A$, $B$, $C$ and $D$ to give the greatest brightness in the light bulb. Which connection should be made ?

Two copper wires, $A$ and $B$, of the same length have the ratio of mass of $4:9$. Assuming the cross-sections are uniform, what is the ratio of the resistance of $A$ to that of $B$ ?

A magnet is allowed to fall through a copper ring. What is the direction of the induced current (if any) on the ring observed by the eye when the magnet is in the position as shown in Figure (1), (2) and (3) ?

The figure above shows how electrical power can be transmitted to a distant factory. The transformers $P$ and $Q$ should be

The diagram shows the label attached to an electric appliance. How much electrical energy is supplied to the appliance in $2$ hours ?

In the circuit above, the two resistors are identical. When the switch $K$ is closed, what happens to the readings of the ammeter $A$ and the voltmeter $V$ ?