Answer: Option A. -> True 
:
A

In a circuit, when a live wire and a neutral wire come into direct contact (shorted), the current in the circuit increases drastically. The current now flows through a low resistive path consisting of wires rather than domestic electric circuits consisting of resistive components. A fuse is a device which prevents the flow of this large amount of current and thus safeguarding the devices against large current.

Answer: Option A. -> Area and number of turns in the coil
:
A, B, and C
The speed of a dc motor can be increased by increasing:

1) The area of the coil.

2) The number of turns of the coil.

3) The magnetic field and current.

Answer: Option D. -> 8
:
D

First cut: 2 north and 2 South Poles.

Second cut: Each of the two pieces were cut into two more pieces.

So, 4 North Poles and 4 South Poles.

Third cut: Each of the 4 pieces is cut into two more pieces.

So, 8 north and 8 South Poles.

Answer: Option A. -> True
:
A

The magnetic force on a current-carrying wire depends on the magnitude of current and the strength of magnetic field. The force is maximum when the direction of current and the field are perpendicular to each other.

Here, the direction of magnetic field is acting downwards, the current carrying wire must be kept horizontal for it to be perpendicular to the magnetic field. Also, this force is minimum (i.e. zero), if the current carrying wire and the field are along the same direction or parallel.

Answer: Option A. -> Clockwise direction
:
A

Using Fleming's right-hand rule, point your index finger of your right hand towards the direction of the magnetic field i.e. from north to south. Middle finger towards the direction of the current. You can now see that the thumb points upwards which tell that the coil rotates in a clockwise direction.

Answer: Option D. -> Hit the wall on the left side of the shooter.
:
D

The answer can be found out using Fleming's left-hand rule:

According to the order: Thumb - Force, Forefinger is Magnetic Field, Middle finger- Current. The direction of current is always opposite to the direction of flow of electrons.

The electrons will move towards the wall which is on the left side of the shooter.

Answer: Option B. -> Joule's heating
:
B

Fuse is a protective device used to disconnect the supply when the current flowing through it exceeds. It is a wire made up of a metal that has low melting point. High current heats and melts it, breaking the circuit.
Joule's heating is the phenomenon that takes place in the fuse which helps it to break the electrical circuit and hence prevents accidents. 

Answer: Option B. -> Magnetic field lines are closed curves.
:
A, B, and D
The direction of the magnetic field is tangent to the field line at any point in space.They originate from the north pole and end at south pole outside the magnet and start at the south pole and ends at the north pole inside the magnet, thus forming a closed curve. The strength of the magnetic field is shown by the degree of closeness of the field lines. Closer the field lines, more the magnetic field strength. Magnetic field lines are closer near the poles, so, magnetic field near the poles is the strongest.

 

Answer: Option A. -> Soft iron
:
A

Soft iron can be used as the core of an electromagnet because it loses all of its magnetism when the current in the coil is switched off. On the other hand, steel retains its magnetism even after the current is switched off.
Brass and aluminium are non-magnetic materials. Hence, they can not be used as the core of an electromagnet.

 

Answer: Option A. -> It will not move.
:
A

The direction of the force on a conductor placed in a magnetic field is given by Fleming's left-hand rule. According to this rule, holding the forefinger, middle finger, and thumb of the left hand in mutually perpendicular directions, the forefinger indicates the direction of the magnetic field and the middle finger, the direction of the current, then the thumb will indicate the direction of the force which results in the motion of the conductor. However, this force is not experienced when the current flows in the direction of the magnetic field. Here, the direction of the current in the conductor and the magnetic field are the same, so, the conductor will not experience any force. Hence, it will not move in any direction.