The diagram below shows four sound waves. Which sound has the highest pitch?

The graph plotted for potential difference (V) against current (I) for ohmic resistors is :

1. A curve passing through the origin.
2. A straight line not passing through origin.
3. A straight line passing through the origin.
4. A circle centred at the origin.

A conductor AB is kept along north south direction of the earth above a magnetic needle as shown below. When the key K is closed then:

1. the needle will not show any deflection.
2. the needle will deflect towards east.
3. the needle will turn in the opposite direction i.e. towards south.
4. the needle will deflect towards west.

A coil wound around a piece of soft iron can become an electromagnet only when:

1. the circuit is open.
2. a magnetic compass is present in the vicinity.
3. a galvanometer is connected to the circuit.
4. a current flows in the circuit.