Magnetic Effect of Electric Current: Overview, Questions, Preparation

An electric current showing the magnetic properties or effects is referred to as an electromagnetic effect. The force that surrounds a magnet is known as the magnetic field.

The strength of a magnetic field depends upon the intensity of the electric current flowing through it. If too many field lines show a magnetic field, it means that its magnetic field is stronger, and similarly, if a few lines are shown, it means that the magnetic field is weak. 

Right-Hand Thumb Rule 

The above image shows the pictorial depiction of the Right-Hand Thumb Rule 

Source: NCERT Class X Textbook

Hold the stick in an upward direction in your palm with your fingers curved around it. Your curled fingers represent the direction in which the field lines are moving in a magnetic field. Now, if you point your thumb upwards along the conductor's length, then it represents the direction of the current flow. This is known as Right-Hand Thumb Rule. 

If the current moves from the north pole to the south pole, the field lines move in the clockwise direction and if the current moves from south pole to north pole then the field lines move in the anticlockwise direction. 

• Two lines of a magnetic field never cross each other. 
• Field lines of a magnetic field are always parallel to one another. 
• As we approach the magnet in a magnetic field, its intensity or strength increases and if we move away from the magnet, its strength decreases.
• When the electric current increases, the magnetic field's magnitude increases. Also, if there is a decrease in the electric current, then its magnitude also decreases. 

An entire chapter is dedicated to this topic in Class X, which carries a weightage of 6 marks. 

You will learn more about this topic in Class XII's chapter 'Moving Charges and Magnetism' where it carries a weightage of 8 marks.

1. An electric appliance of 3kW power rating is operated at 150V. Find the current flowing through it.

Solution:

Power = 3kW = 3000W 

V = 150V 

The formula to calculate current is given below:

I = P/V = 3000/150 = 20A

2. How much voltage is required to operate an electric appliance of 20W power rating if the current flowing through the circuit is 10A?

Solution:

We have the formula, P = VI. 

Therefore, V = P/I = 20/10 = 2V.

3. What will happen if an electric circuit of 150W power rating is operated at 30V if its current rating is 3A?

Solution:

First, to find the electric current flowing through the circuit, we have the formula:

I = P/V = 150/30 = 5A 

The current rating is 3A, but an electric current of 5A is flowing through the circuit. Therefore, the fuse will get damaged due to melting, and the circuit will shut down immediately.