Magnetic Effects of Electric Current

State the factors on which the strength of magnetic field at a point due to a current carrying conductor depends. State the rule which gives the direction of magnetic field.

A student performs an experiment to study the magnetic effect of current around a current carrying conductor with the help of a magnetic compass. He reports that:

• The degree of deflection of the magnetic compass increases when the compass is moved away from the conductor.
• The degree of deflection of the magnetic compass increases when the current through the conductor is increased

Which of the above observations of the student appears to be wrong and why?

Define a magnetic field line?

Or

What are magnetic field lines?

For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

(a) Both A and R are true, and R is correct explanation of the assertion.

(b) Both A and R are true, but R is not the correct explanation of the assertion.

(c) A is true, but R is false.

(d) A is false, but R is true.

Assertion: In a conductor, free electrons keep on moving but no magnetic force acts on a conductor in a magnetic field.

Reason: Force on free electron due to magnetic field always acts perpendicular to its direction of motion.

How is the direction of magnetic field at a point determined?

A magnetic compass is placed near a current carrying wire. What will you observe?

• When current in the wire is increased,
• When the magnetic compass is displaced away from the wire?

Or

A magnetic compass shows a deflection near a current carrying wire. How will the deflection of the compass get affected if current in the wire is increased? Support your answer with reason.

What is meant by magnetic field?

For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

(a) Both A and R are true, and R is correct explanation of the assertion.

(b) Both A and R are true, but R is not the correct explanation of the assertion.

(c) A is true, but R is false.

(d) A is false, but R is true.

Assertion: No net force acts on a rectangular coil carrying a steady current when suspended freely in a uniform magnetic field.

Reason: Forces acting on each pair of the opposite sides of the coil are equal and opposite.

Give two uses of a magnetic compass.