Physics [1 Mark Question Answer]

Mechanical energy changes into the electrical energy.

The core of a transformer is laminated to reduce the energy loss due to eddy currents.

No, a transformer cannot work on a d.c. source. With a d.c. source, there will be no change in magnetic flux linked with the secondary coil.

We use a step-up transformer to push up or step up the voltage of a given a.c. source.

The functioning of a transformer depends on the phenomenon of electromagnetic induction.

The frequency of the alternating e.m.f. depends on the frequency of rotation of the coil.

A transformer is device by which the amplitude of an alternating e.m.f. can be increased or decreased.

Dynamo (or a.c. generator) is a device which converts mechanical energy into electrical energy. It works on the principle of electromagnetic induction.

(i) The time of change of magnetic flux, (ii) The strength of magnetic field.

Electromagnetic induction: whenever there is change in number of magnetic field lines associated with conductor, an electromotive force is developed between the ends of the conductor which lasts as long as the change is taking place.

The deflecting couple acting on the coil is minimum when the plane of the coil is normal to the direction of magnetic field.

The deflecting couple acting on the coil is maximum when the plane of the coil is parallel to the direction of magnetic field.

The energy change that takes place in a D. C. motor is from electrical energy into mechanical energy.

Electrical energy to mechanical energy.

Direction of force is also reversed.

The material used for making the armature of an electric bell is soft iron which can induce magnetism rapidly.

Electromagnets are used in electric bell, door alarm, motor, dynamo etc.

If electric bell is connected to a.c. instead of d.c. then bell will ring intermittently.

Electromagnet can produce a strong magnetic field. Its polarity can be changed by reversing the direction of current.

A permanent magnet is a magnet made from steel such that once magnetized, it does not lose its magnetism easily. Use: It is used in the galvanometer.

When an electric charge flows in a conductor, a magnetic field is produced around it.

The lines of force, in this case, are concentric circles centered on the wire.

By decreasing the current flowing in the solenoid, the intensity of magnetic field decreases.

By placing a soft iron core inside the solenoid, the magnetic field becomes more intense.

By having a solenoid of large diameter or more cross-sectional area, the intensity of magnetic field increases.

By having more number of turns, the intensity of magnetic field increases.

A current carrying conductor is associated with a magnetic field around it.

The purpose of the iron core is to intensify the strength of the magnetic field inside the solenoid and thereby increase the strength of the electromagnet.

A moving charge is associated with a magnetic field around it.

This force F is zero when the magnetic field due to flow of current in the conductor is parallel to the given magnetic field B.

This force F is maximum when the magnetic field due to flow of current in the conductor and the given magnetic field B are perpendicular to each other.

A static charge is not associated with a magnetic field around it.