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5. Class 10th Science Chapter 13 Magnetic Effects of Electric Current-

# Class 10th Science Chapter 13 Magnetic Effects of Electric Current-

Question 1. What is an alternating current called?
Answer: The electric current which changes its direction after equal intervals of time is called alternating current.

Question 2. On what principle does an electric generator work?
Answer: Electric generator works on the principle of electromagnetic induction.

Question 3. What is the main function of an electric generator?
Answer: The main function of an electric generator is to convert mechanical energy into electrical energy.

Question 4. What is the main function of electric motor.
Answer: The main function of an electric motor is to convert mechanical energy into electrical energy.

Question 5. On what principle does an electric motor work?
Answer: When an electric current is passed through a coil made of conducting wire located inside a magnetic field, a pair of forces acts on the coil, due to which the coil starts rotating within the magnetic field. This is the principle of the electric motor.

Question 6. How is an electromagnet made?
Answer: When current is passed by keeping a soft iron rod inside a solenoid, it behaves like a strong magnet. This type of arrangement is called electromagnet.

Question 7. Give two examples of use of electric motor.Answer: The working of both flour mill and washing machine is based on electric motor.

Question 8. What is meant by magnetic field lines?
Answer: Magnetic field lines are imaginary curved lines drawn in a magnetic field on which the independent magnetic north pole moves.

Question 1. List the properties of magnetic field lines.
Answer: The following are the properties of magnetic fields or lines of force
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(1) The direction of these lines of force outside the magnet is from the north pole to the south pole and inside the magnet from the south pole to the north pole. Thus it is in the form of a closed curve.
(2) The tangent drawn at any point to the magnetic field of force represents the direction of the magnetic field at that point.
(3) Magnetic lines of force never intersect because two directions of magnetic field are not possible at the same point.

Question 2. Write Fleming’s right hand rule.
Answer- Fleming’s Left Hand Rule: Spread the thumb, forefinger and middle finger of your left hand in such a way that they are perpendicular to each other. The index finger will indicate the direction of the magnetic field and the middle finger will indicate the direction of flow of current and the thumb will indicate the direction of the conductor. This rule is called Fleming’s Left Hand Rule.

Question 3. State two differences between alternating current and direct current.
Answer: Direct current always flows in one direction, whereas alternating current keeps reversing its direction after a certain time interval.

Question 1. How does a current carrying solenoid act like a bar magnet?
Answer: The similarity of a current-carrying solenoid to a bar magnet-

(1) When both the bar magnet and the current carrying solenoid are hung freely, they stop in good north and south direction of both.
(2) Both the bar magnet and the current carrying system attract small pieces of iron towards themselves.
(3) The needle gets deflected when the compass needle is brought near both the bar magnet and the current carrying solenoid.

Question 1. Draw a labeled diagram of an electric motor. Explain its principle and working. What is the significance of the dividing ring in an electric motor?

electric motor-An electric motor is a device that converts electrical energy into mechanical energy.

Theory-When a coil is placed in a magnetic field, current is passed through it. So a pair of forces starts acting on the coil, which starts rotating the coil if it is free to rotate on its axis.