Ncert – class 10- science – Chapter 12 – Magnetic Effects of Electric Current 2 Welcome to your Ncert - class 10- science - Chapter 12 – Magnetic Effects of Electric Current 2 1. A DC current flows through a vertical wire in the downward direction. For an observer looking at the wire, the direction of magnetic field at a point between him and the wire is: To the left To the right Downward Upward None 2. In a circular current-carrying conductor, if the current flows in the clockwise direction, the magnetic field direction is __________. Parallel to the coil towards the observer Parallel to the plane of the coil away from the observer Perpendicular to the plane of the coil away from the observer Perpendicular to the plane of the coil towards the observer None 3. None 4. The phenomenon of producing an emf in a circuit whenever the magnetic flux linked with a coil changes is ................................ Inducing current Inducing voltage Change in current Electro-magnetic induction None 5. The magnetic field around a current-carrying coil lasts For three hours Field is permanent Till its half-life period As long as current flows through it None 6. Consider an experiment where Electric current is flowing in a wire. It is observed that clockwise magnetic field is produced around the wire. A teacher decides to reverse the direction of source battery which results in reversal of electrical current. What will be the effect on magnetic field? Field lines changes direction to parallel to wire Direction of field lines reverse None of the above Magnetic field disappears None 7. Household appliances are usually not connected in series because: The appliances would get damaged due to high current Switching off an appliance would switch off the rest Power consumption would be very much greater A fuse would blow as soon as one appliance is used None 8. A length of wire carries a steady current. It is bent first to form a circular plane coil of one turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre caused by the same current is Half of its first value Four times of its first value Unaltered Quarter of its first value None 9. Current is flowing through a conductor and creates a magnetic field. Assume that this is the only source of the magnetic field. Reversing a current in a straight conductor with no change to the magnitude(ampere value) will cause a _________. Reversal of the direction of the magnetic field Reversal and reduction of the magnetic field Disappearance of the magnetic field Reduction in the magnetic field None 10. In alternating current: The direction of current is always negative The direction of current changes constantly None of these The direction of current is always positive None 11. Which of the following electrical devices works on the principle of electro-magnetic induction ? Electric bulb L.E.D. Electric cooker Electric fan None 12. What is a commutator? A device that flows in the direction of flow of current through a circuit is called a commutator. A device that reverses the direction of flow of voltage through a circuit is called a commutator. All of these A device that reverses the direction of flow of current through a circuit is called a commutator. None 13. The magnetic field around a current carrying coil Lasts as long as current flows through it Lasts till its half-life period Lasts for three hours Is permanent None 14. A soft bar is inserted inside a current carrying solenoid. The magnetic field inside the solenoid. Will remain the same Will decrease Will become zero Will incresae None 15. A beam of protons is moving horizontally towards you. As it approaches you, it passes through a magnetic field which is directed upwards. As you see it, the magnetic field will deflect the beam to the: Top Right Bottom Left None 16. Which one of the following statements best describes the nature of the field lines due to a bar magnet? Field lines start from the north pole and end on the south pole. Any number of field lines can pass through a point Field lines are continuous lines passing inside and outside the magnet. Any number of field lines can pass through a point Field lines are continuous lines passing inside and outside the magnet. Only one field line passes through a point Field lines start from the north pole and end on the south pole. Only one field line passes through a point None 17. A charge particle is moving in the direction of a magnetic field.The magnetic force acting on the particle: is zero is in the direction opposite to its velocity is perpendicular to its velocity is in the direction of its velocity None 18. As a negatively charged bowling ball rolls eastward toward some bowling pins, in what direction does it experience a force, due to the earth's magnetic field (Assume the earth's field is pointing straight north)? Down South East North None 19. Why is the switch for any electrical appliance always fitted on to the live wire ? The device can never be switched off if the switch is in the neutral lead. No current flows in the neutral wire. The device can only be isolated if the switch is in the live lead There will be a short circuit if the switch is in the earth lead. None 20. A straight wire carries conventional current toward the sky.What is the direction of the magnetic field due to the current at a point west of the wire? 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