What are superconductors?

Conductors exhibit a phenomenon known as superconductivity at a very low temperature known as critical temperature. At the critical temperature, a metal offers zero resistance to the passage of electric current through them. These types of conductors are called superconductors.

When a current carrying conductor is placed in a magnetic field, it experiences a mechanical force. What should be the angle between the magnetic field and the length of the conductor so that the force experienced is: (i) Zero (ii) Maximum

When a current-carrying conductor is placed in a magnetic field, it experiences a force, which can make the conductor move from its actual position. From the expression F = B I L sin θ , where ' F ' is the mechanical force experienced by the conductor, ' B ' is the magnetic field, and ' L ' is the length of the conductor, and ' θ ' is the angle between the direction magnetic field and the electric current. (i) If θ = 0 ° , then the force experienced will be zero as sin 0 ° = 0 . (ii) If θ = 90 ° , then the force experienced will be maximum F = B I L sin 90 ° = B I L × 1 F = B I L . Therefore, the angle between the magnetic field and the length of the conductor so that the force experienced is zero should be 0 ° , and for maximum force it should be 90 ° .

On which type of current do transformers work?

A transformer is a device that is used to change the AC (alternating current) voltage. It converts low voltage at high current to a high voltage at low current. A transformer works on the principle of mutual induction. A transformer does not work on DC.

How is the emf across primary and secondary coils of a transformer related with the number of turns of coil in them?

We know, E s E p = N s N p Where, E s & E p are the emf across the secondary and the primary coils respectively and N s & N p are the number of turns in the secondary and the primary coils respectively. A transformer works on the principle of mutual induction. Here emf is directly proportional to number of turns.

The diagram below shows a magnetic needle kept just below the conductor AB which is kept in the North-South direction. i) In which direction will the needle deflect when the key is closed? ii) Why is the deflection produced? iii) What will be the change in the deflection if the magnetic needle is taken just above the conductor AB? iv) Name one device which works on this principle.

According to the Right-Hand Thumb Rule for the magnetic field, when we hold a current-carrying conductor in the right hand, where the thumb points towards the direction of the current. When we wrap the fingers around the conductor, the fingers point towards the direction of the magnetic field lines. i) In the first case, when the key is closed the current is from B to A. So, as per the right-hand thumb rule just below the conductor, the direction of the magnetic field is towards east. So, due to this needle will deflect towards east. ii) The deflection is produced due to the magnetic field created when current is passed through the wire. iii) In the second case when a magnetic needle is kept just above the conductor when the key is closed the current direction will reverse i.e. from B to A. So, applying right-hand thumb rule just above the conductor, the direction of the magnetic field generated is towards west. So, the needle will deflect towards the West. iv) A device that works on this principle is a magnetic sensor.

Draw a neat labeled diagram of an A.C. generator.

An A.C. generator is a device that converts mechanical energy into electrical energy and produce electricity. It works based on electromagnetic induction.