# CBSE – 10th Standard Science

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### Class 10 Question Bank Chapter 13 – Magnetic effects of electric current

Q1 Why does a compass needle get deflected when brought near a bar magnet

Ans. The compass is a small magnet and like poles repel each other and unlike poles attract each other, so it deflects when brought near a bar magnet.

Q2. List the properties of magnetic lines of force.

Ans, Magnetic field has direction and magnitude. The force increases as current is increased.

Q3. Why don’t two magnetic lines of force intersect each other?

Ans. Because at intersecting point the needle will show two directions which is not possible

Q4. What is the use of magnetism in medical line?

Ans. The magnetic field inside the body forms the basis of obtaining the images of different body parts. Magnetic Resonance Imaging (MRI) analysis of these images helps in medical diagnosis.

Q5. State Fleming’s left-hand rule.

Ans. .According to Fleming’s left-hand rule stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.

Q6. How is electric current induced  in a coil.

Ans. The change in magnetic field lines associated with the coil is the cause of induced electric current in it.

Q7 .What is the principle of an electric motor?

Ans.  An electric motor is a device that converts electric energy into mechanical energy, A current-carrying conductor when placed in a magnetic field experiences a force. If the direction of the field and that of the current are mutually perpendicular to each other, then the force acting on the conductor will be perpendicular to both, it is the basis of motor.

Q8. What is the role of the split ring in an electric motor?

Ans.  In electric motors, the split ring acts as a commutator which reverses the direction of flow of current through a circuit .

Q9. State the principle of an electric generator.

Ans.. A generator converts mechanical energy into electrical energy. It works on the basis of electromagnetic induction that produces induced current in a coil placed in a region where the magnetic field changes with time.

Q10. Name sources of direct current, alternating current?

Ans.  A generator produces DC and most power stations produce Ac.

Q11.  who studied  first that moving magnet can be used to generate electric currents

Ans. This was first studied by English physicist Michael Faraday. In 1831, Faraday discovered that moving magnet can be used to generate electricity.

Q12. Name two safety measures commonly used in electric circuits and appliances.

Ans Three colored  wires with earthing and Fuse are safety measures commonly used in electric circuits and appliances

Q13. What precaution should be taken to avoid the leakage and overloading of domestic electric circuits?

Ans. Fuse and earth wire are  the most important safety device, used for protecting the circuits due to short-circuiting or overloading of the circuits.

Q14. What is the function of an earth wire? Why is it necessary to earth metallic appliances?

Ans. The earth wire is connected to a metallic body deep inside earth to protect from leakage of current this prevents shock to user.

Q15. List two methods of producing magnetic fields.

Ans. Magnetic fields are produced by magnets and an electric current flowing through a conductor produces a magnetic field.

Q16 Who was the first to find force on a current carrying conductor in a magnetic field?

Ans.  French scientist Andre Marie Ampere firstly suggested that the magnet must also exert an equal and opposite force on the current-carrying conductor.

Q17. How does a solenoid behave like a magnet?

Ans. The field inside a solenoid is same and parallel thus one end behaves like south pole and other behaves like north pole of a magnet.

Q18. When is the force experienced by a current–carrying conductor placed in a magnetic field largest?

Ans. The magnitude of the force is the highest when the direction of current is at right angles to the direction of the magnetic field.

Q19. What is the use of solenoid in making electromagnet?

Ans. A strong magnetic field produced inside a solenoid can be used to magnetise. A piece of magnetic material, when placed inside the coil magnet is formed is called an electromagnet.

Q20. Name some devices in which electric motors are used.

Ans. Electric motor is used as an important component in electric fans, refrigerators, mixers, washing machines, computers, MP3

Q21. When does an electric short circuit occur?

Ans. Insulation of wires is damaged or there is a fault in the appliance, the current in the circuit abruptly increases this is called short-circuiting.