The magnetic field inside a long straight solenoid-carrying current

1

(a)

is zero

(b)

decrease as we move towards its end

(c)

increases a swe move towards its end

(d)

is the same at all points.

Which of the following correctly describes the magnetic field near a long straight wire ?

1

(a)

The field consists of straight lines perpendicular to the wire.

(b)

The field consists of straight lines Parallel to the wire.

(c)

The field consists of radial lines originating from the wire.

(d)

The field consists of concentric circles centred on the wire.

The phenomenon of electromagnetic induction is 

1

(a)

the process of charging a body.

(b)

the process of generating magnetic field due to a current passing through a coil.

(c)

producing induced current in a coil due to relative motion between a magnet and the coil.

(d)

the process of rotating a coil of an electric motor.

The essential difference between an AC generator and a DC generator is that

1

(a)

AC generator has an electromagnet while a DC generator has permanent magnet.

(b)

DC generator will generate a higher voltage.

(c)

AC generator will generate a higher voltage

(d)

AC generator has slip rings while the DC generator has a commutator.

At the time of short circuit, the current in the circuit

1

(a)

reduces substantially

(b)

does not change

(c)

increases heavily

(d)

vary continuously

Commercial electric motors do not use

1

(a)

An electromagnet to rotate the armature

(b)

Effectively large number of turns of conducting wire in the current carrying coil

(c)

A permanent magnet to rotate the armature

(d)

A soft iron core on which the coil is wound

Choose the incorrect statement

1

(a)

Fleming's right-hand rule is a simple rule to know the direction of induced current.

(b)

The right-hand thumb rule is used to find the direction of magnetic fields due to current carrying conductors.

(c)

The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically.

(d)

In India, the AC changes direction after every 1/50 second.

The strength of magnetic field inside a long current carrying straight solenoid is 

1

(a)

More at the ends than at the centre

(b)

Minimum in the middle

(c)

Same at all points

(d)

Found to increase from one end to the other.

To convert an AC generator into DC generator

1

(a)

Split-ring type commutator must be used

(b)

Slip rings and brushes must be used 

(c)

A stronger magnetic field has to be used

(d)

A rectangular wire has to be used.

The most important safety method used for protecting home appliances from short circuiting or overloading is

1

(a)

Earthing

(b)

Use of fuse

(c)

Use of stabilisers

(d)

Use of electric meter.

What does an electric current carrying wire behaves like?

1

(a)

It behaves like a magnet.

Distinguish between DC and AC.

1

(a)

DC	AC
1. Unidirectional flow of current.	Current changes its direction in a cycle.
2. Cells and batteries produce DC.	Dynamo produces AC.

Name the device that converts electric energy into mechanical energy.

1

(a)

An electric motor.

Define electromagnetic induction.

1

(a)

The phenomenon in which an electric current is induced in a circuit because of a changing magnetic field is called electromagnetic induction.

What is galvanometer?

1

(a)

A galvanometer is an instrument that can detect the presence of a current in a circuit.

Name the rule used to determine the direction of induced current.

1

(a)

Direction of induced current is given by Fleming's right hand rule according to this rule, stretch the thumb, fore-finger and the middle finger of the right hand such that they are mutually perpendicular.
If the fore-finger points in the direction of magnetic field the thumb shows the direction of motion and middle finger points in the direction of induced current.

What is the difference between AC generator and DC generator?

1

(a)

AC generator produces current which changes its direction after equal intervals of time and DC generator produces current which is unidirectional.

What are concentric circles?

1

(a)

The magnetic field lines around a straight conductor carrying current are concentric circles.

What is similar between solenoid and bar magnet?

1

(a)

The magnetic field produced by a solenoid is similar to the bar magnet.

What is the use of electric fuse?

1

(a)

Electric fuse is used for protecting the circuits due to short circuiting or overloading of the circuits.

Why does a compass needle get deflected when brought near a bar magnet?

2

(a)

List the properties of magnetic lines of force.

2

(a)

Why do not two magnetic lines of force intersect each other?

2

(a)

The magnetic field in a given region is uniform. Draw a diagram to represent it.

2

(a)

State Fleming's Left hand Rule.

2

(a)

On what principle does electric motor work?

2

(a)

What is the role of a split ring in an electric motor ?

2

(a)

Name some sources of direct current.

2

(a)

Name two safety measures commonly used in electric circuits and appliances.

2

(a)

Two circular coils A and B are placed close to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.

2

(a)

With the help of a labelled circuit diagram illustrate the pattern of field lines of the magnetic field around a current carrying straight long conducting wire. How is the right hand thumb rule useful to find direction of magnetic field associated with a current carrying conductor?

5

(a)

Explain with the help of a labelled diagram the distribution of magnetic field due to a current through a circular loop. Why is it that if a current carrying coil has 'n' turns the field produced at any point is n times as large as that produced by a single turn?

5

(a)