Chapter 13 Magnetic Effects of Electric Current Solutions
Question - 11 : - ng’s left-hand rule.
Answer - 11 : - Fleming’s Left hand rule states that if we arrange our thumb, forefinger and middle finger of the left hand at right angles to each other, then the thumb points towards the direction of the magnetic force, the forefinger points towards the direction of magnetic field and the middle finger points towards the direction of current.
Question - 12 : - What is the principle of an electric motor?
Answer - 12 : - The working principle of electric motor is based on the magnetic effect of current. A current carrying conductor when placed in a magnetic field experiences force and rotates. The direction of the rotation of the conductor can be determined by Fleming’s Left hand rule.
Question - 13 : - What is the role of split ring in an electric motor?
Answer - 13 : - Split ring plays the role of commutator in an electric motor. The commutator reverses the direction of the current flowing through the coil after each half rotation of the coil. Due to this reversal of current, the coil continues to rotate in the same direction.
Question - 14 : - Explain different ways to induce current in a coil.
Answer - 14 : -
Following are the different ways to induce current in a coil:
• If the coil is moved rapidly between the two poles of horse shoe magnet, electric current is induced in the coil.
• When a magnet is moved relative to the coil, an electric current is induced in the coil.
Question - 15 : - State the principle of an electric generator.
Answer - 15 : - Electric generator works on the principle of electromagnetic induction. In a generator, electricity is generated by rotating a coil in the magnetic field.
Question - 16 : - Name some sources of direct current.
Answer - 16 : - DC generator and cell are some sources of direct current.
Question - 17 : - Which sources produce alternating current?
Answer - 17 : - Power plants and AC generators are some of the sources that produce alternating current.
Question - 18 : - Choose the correct option.
A rectangular coil of copper wires is rotated in a magnetic field.
Answer - 18 : -
The direction of the induced current changes once in each
1. two revolutions 2. one revolution
3. half revolution 4. one-fourth revolution
Answer
c. half revolution
When a rectangular coil is rotated in magnetic field, the direction of the induced current changes once in half revolution. As a result, the direction of the current in the coil remains the same.
Question - 19 : - Name two safety measures commonly used in electric circuits and appliances.
Answer - 19 : -
The safety measured commonly used in electric circuits are as follows:
1. Fuse
Each circuit should be connected to a fuse because a fuse prevents the flow of excessive current through the circuit. When the current in the circuit exceeds the maximum limit of the fuse element, the fuse melts to stop the flow of current protecting the appliance connected to circuit.
1. Earthing
Earthing protects the user from electric shocks. Any leakage of current in an appliance is transferred to the ground by earthing and the people using the appliance is prevented from getting electrocuted.
Question - 20 : - An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.
Answer - 20 : -
The current drawn by the electric oven can be calculated using the formula
P = V × I
I = P/V
Substituting the values, we get
I = 2000 W/220 V = 9.09 A
The current drawn by the electric oven is 9.09 A which exceeds the safe limit of the circuit. This causes the fuse to melt and break the circuit.