 Magnetic Effect of Electric Current class 10 science NCERT In Text solution part 1

# Electromagnetism

## In Text Solution 1

List the properties of magnetic lines of force.

Answer: Properties of magnetic field lines:

• Magnetic field lines follow the direction from the north pole to the south pole.
• Magnetic field lines always show concentric pattern.
• Magnetic field lines do not cross one another.
• Closer the field lines; stronger is the magnetic field and vice-versa is also true.
• Magnetic field lines are closer near the poles; which shows greater strength of magnetic field near the poles.

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

Answer: When a compass needle is brought near a bar magnet, the compass needle experiences a deflection. This happens because of interaction of magnetic fields of the compass needle and the bar magnet.

Draw magnetic field lines around a bar magnet. Why don’t two magnetic lines of force intersect each other?

Answer: The direction of magnetic field lines is always from the north pole to the south pole. If the field lines would cross each other then the direction of field line would change at the point of crossing which is practically impossible. Hence, two magnetic field lines never intersect each other.

Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right hand rule to find out the direction of the magnetic field inside and outside the loop.

Answer: As the given figure shows; current is flowing clockwise through a circular loop. The direction of magnetic field around the conductor can be known by using the right hand thumb rule. As the figure shows, the magnetic field would be towards the plane of the paper when it is inside the loop. On the other hand, the magnetic field would be away from the paper when it is outside the loop. The magnetic field in a given region is uniform. Draw a diagram to represent it. The magnetic field inside a long straight solenoid-carrying current

1. Is zero
2. Decreases as we move towards its end
3. Increases as we move towards its end
4. Is the same at all points

Answer: (d) Is the same at all points

Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer)

1. Mass
2. Speed
3. Velocity
4. Momentum

Answer: (c) and (d), i.e. velocity and mass of proton change when it enters a magnetic field. When a proton enters a magnetic field it starts moving on a circular path. Because of its movement along a circular path it attains angular momentum. We know that momentum is a product of mass and velocity.

In Activity 13.7, how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased?

Answer: In this case, the displacement would vary directly as the strength of current, strength of magnetic field and length of the conductor. Due to this, the displacement of conductor would be increased in all the three cases.