Science 5 Marks Questions

The bulb in the circuit is not glowing because the two cells are not connected properly.

To make the bulb glow, the negative terminal of one cell should be connected to the positive terminal of the other cell, as shown in the given figure.

To make a battery, the negative terminal of one cell must be connected to the positive terminal of the next cell. The wire indicates the manner in which the given cells should be connected with each other, as shown in the following figure.

In the given circuit, one terminal of the bulb is connected with one terminal of the cell while their other terminals are connected to a safety pin. However, the safety pin is not connected with one of the drawing pins. Thus, the circuit is not complete. Hence, safety pin represents a switch in ‘OFF’ position. The circuit diagram of the given figure is shown in the following figure

In the given circuit, one terminal of the bulb is connected with one terminal of the cell while their other terminals are connected to a safety pin. However, the safety pin is not connected with one of the drawing pins. Thus, the circuit is not complete. Hence, safety pin represents a switch in ‘OFF’ position. The circuit diagram of the given figure is shown in the following figure.

Following are the points of difference between an electric motor and a generator:Electric Motor:

• It converts electrical energy into mechanical energy.
• It needs electrical energy for its working.
• They are used as water pumps, marble grinders etc.

Generator:

• It converts mechanical energy into electrical energy.
• It needs mechanical energy for its working.
• They are used as water pumps, marble grinders etc.
• Diesel generator, hydro-electric generator are the examples of it.

The properties of magnetic field due to a current flowing through a straight wire are:

1. The magnitude of the magnetic field produced at a given point increases as the current through the wire increases.
2. The magnetic field produced by a given current in the conductor decreases as the distance from it increases.
3. The concentric circles representing the magnetic field around a current-carrying straight wire become larger and larger as we move away from it.
4. If the direction of the current is reversed in the wire, the lines will still be circular, but the directions of the lines will be reversed, which can be verified using the compass needle.

In order to ring the bell first of all we press the push button switch in order to ring the bell. So, when we press the switch, then the electric circuit of the bell is completed and a current passes through the coil of the electromagnet and it gets magnetised. The electromagnet attracts the iron armature towards itself. So, as the armature moves towards the poles of the electromagnet, the clapper attached to it strikes the gong and produces a ringing sound. It implies that the bell rings. When the armature moves towards the magnet, its contact with the contact screw is broken. Due to this, the electric circuit breaks and no current flows in the electromagnet coil. The electromagnet loses its magnetism for a moment and the armature is no longer attracted by it. The flat spring brings back the iron armature to its original position and the clapper also moves away from the gong. As soon as the armature comes back and touches the contact screw the circuit is completed and current starts flowing in the electromagnet coil again. The electromagnet attracts the iron armature once again and the clapper strikes the gong again producing a ringing sound. So, this process of 'make and break' of the electric circuit continues as long as we are pressing the switch. Due to this, the armature vibrates forwards and backwards rapidly each time making the clapper strike the gong. Thus, the clapper strikes the gong rapidly producing almost continuous sound.

Following are the characteristics of magnetic field line:

• They represent the magnetic field.
• They are directed from north to South Pole outside a magnet and from south to North Pole inside a magnet.
• The field lines are closed curves.
• The strength of magnetic field in a region is determined by closeness of the field lines in that region.
• The closer the field lines are, greater will be the field strength and vice-versa.
• No two field lines ever cross each other as it would mean two different directions of field at point of intersection, which is not possible.
• The parallel lines represent the uniform magnetic field whereas converging lines or diverging lines represents the non-uniform magnetic field.