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Part (a) : 3 Marks
Part (b) : 2 Marks
(a) The two effects of electric current are:
1) Heating effect of current: When an electric current passes through awire, the electrons in the wire starts vibrating more vigorously due to which wire gets heated. This is known as the heating effect of current. It is used in many appliances like electric heater,electric bulb etc.
2) Magnetic effect of current: when an electric current flows through a wire, it produces magnetic effect around it. This effect is called the magnetic effect of current. If current carrying wire is wrapped around a piece of iron, the iron piece acts as an electromagnet. The magnetic effecthas many applications like power lift, electric bell etc.
(b) Whencurrent flows through a wire, the wire starts behaving as a magnet. Hence, when a compass needle is placed near the given current carrying wire, it gets influenced by the magnetic effect of electric current and gets deflected from its North-South position.

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Each part: 1Mark
(a) For changing the direction in which magnetic needle gets deflected, we have to reverse the direction of current flowing in the wire. This can be achieved by changing the polarity of the battery.
(b)Magnetic field lines give the direction of magnetic field around a conductor. So the pattern of field lines is similar to that of iron fillings, i.e. concentric circles. The figure below shows the magnetic field lines around a current carrying conductor.

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Reason: 1 Mark
Phenomenon: 1 Mark
We should not touch a lighted bulb because it may be warm and cause injury.
The bulb gets hot due to the heating effect of electric current.

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Definition: 1Mark
Applications: 2 Marks
When an electric current flows through a wire, the wire gets heated. It is the heating effect of current. This effect has many applications.
A filament is a thin wire inside a bulb which produces light.It is a kind of resistor. When electricity passes through the material, the filament gets heated, it glows producing light.
Various other electrical appliances where this principle is used are iron, electric heater, etc.

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Each question: 2 Marks
An electromagnet is a type of magnet in which themagnetic field is produced by an electric current. The magnetic field disappears when the current is turned off. A current-carrying coil or an insulated wire wrapped around a piece of iron behaves like anelectromagnet.
Two methods by which we can increase the strength of magnetic field are:
1) By increasing the number of turns of wire in the coil.
2) By increasing the current flowing in the coil.

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An ammeter is used to measure electric current in an electric circuit.

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Fuses: 1.5 Marks
Alternative: 0.5 Marks
Electrical fuses are wires made from special materials that melt quickly and break when large electric current is passed through them.
There is a maximum limit of current which can safely pass through the circuit.
When a large amount of current passes through the circuit it may cause damage to various electric appliances.
The appliances may also catch fire due to short-circuit.
So, fuses are used for safety purposes.
MCBs can be used instead of fuses.

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Reason: 2 Marks
Preventive measure: 1 Mark
The various reasons due to which there may be excessive current in electric circuits are:
1) Direct touching of wires. This may happen if the insulation on the wires has come out due to wear and tear. This may cause a short circuit.A short circuit can result in a very highcurrentflowing through the circuit.
2) Another reason for excessive current can be the connection of many devices to a single socket. This may cause overload in the circuit.
We can prevent excessive current in electric circuits by using a fuse, or MCBs.

Answer: Option B. -> False
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B
Electric bell works on the magnetic effect of electric current. An electric bell consists of an electromagnet, a striker and a gong. When the circuit is closed, the electromagnet attracts the striker towards it. The striker hits the gong and produces a sound.

Answer: Option B. -> For the protection of electrical appliances and circuit.
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B
Fuse wire is used in electric circuits to prevent the excess current flowing into the circuit and therefore preventing the appliances from getting damaged.