Q.1. Name the type of current: (a) used in household supply. (b) given by a cell.
Answer. (a) Alternating current. (b) Direct current.
Q.2. State the observation made by Oersted on the basis of his experiment with current carrying
conductors.
Answer. The electric current passing through a conducting wire produces magnetic effect.
Q.3. How will you determine the direction of the magnetic field due to a current-carrying
solenoid in the below diagram?
Answer. Direction of magnetic field: Imagine the current carrying solenoid in your right hand
such that the curled fingers are in the direction of current, then the extended thumb will indicate
the direction of emerging magnetic field line, i.e. the face of solenoid which has North polarity.
Q.4. A steady current of 5 A is flowing through a conductor AB. Will the current be induced in
the circular wire of radius 1m?
Answer. No, because circular coil is placed in a constant magnetic field produced by a steady
current of 5A.
Q.5. Name the device used to prevent damage to the electrical appliances and the domestic
circuit due to overloading.
Answer. Electric fuse.
Q.6. Give one difference between the wires used in the element of an electric heater and in a fuse.
Answer. Electric wire used in electric heater has a high melting point whereas fuse wire has a low
melting point.
Q.7. The diagram shows a beam of electrons about to enter a magnetic field. The direction of the
field is into the page. What will be the direction of deflection, if any, as the beam passes through the field?
Answer. Direction of current is from right to left as electron beam enters from left to right and
magnetic field is into the page. So, according to Fleming’s left hand rule, force is perpendicular to the flow of current and in its left side. So, electron beam deflects towards bottom of the page.
Q.8. How can you show that the magnetic field produced by a given electric current in the wire
decreases as the distance from the wire increases?
Answer. The decrease in deflection of the magnetic compass needle clearly shows that the
magnetic field decreases as we move away from the current-carrying conductor.
Q.9. A current carrying straight wire held perpendicular to the plane of paper and current passes through this conductor in the vertically upward direction. What is the direction of magnetic field produced around it?
Answer. According to right-hand thumb rule, the direction of magnetic field produced around the given conductor is anticlockwise.
Q.10. An electron beam is moving vertically upwards. If it passes through a magnetic field which
is directed from south to north in a horizontal plane, then in which direction will the beam
deflect?
Answer. Using Fleming’s Left-Hand Rule, electron beam will be deflected towards the west.
Q.11. A charged particle enters at right angle into a uniform magnetic field as shown. What
should be the nature of charge on the particle if it begins to move in a direction pointing
vertically out of the page due to its interaction with the magnetic field?
Answer. Using Fleming’s left hand rule, the nature of charged particle is positive.
Q.12. Name the device which is used to draw magnetic field lines.
Answer. Compass needle.
Q.13. Identify the poles of the magnet in the given figure.
Answer. Both the poles facing each other represent south pole in nature as the magnetic field
lines outside the magnet move from North to South Poles.
Q.14. State the direction of magnetic field in the following case.
Answer. In given situation, according to Fleming’s Left-Hand Rule Force is along y-axis. Current
is along x-axis. Then magnetic field is along z-axis.
Q.15. State the direction of magnetic field in the following case.
Answer. Perpendicular to the plane of paper in the outward direction by using Fleming’s left
hand rule.
Q.16. Give one application of electromagnetic induction.
Answer. This phenomenon is used in electric generator.
Q.17. Name the physical quantities which are indicated by the direction of thumb and forefinger
in the Fleming’s right hand rule?
Answer. In Fleming’s right hand rule, thumb indicates — direction of motion of the conductor; forefinger indicates — direction of magnetic field.
Q.18. A positively charged particle (alpha-particle) projected towards west is deflected towards
north by a magnetic field. The direction of magnetic field is
(a) towards north (b) towards east
(c) downward (d) upward
Answer. (d) Upward (Apply Fleming’s left hand rule).
Q.19. The diagram shows a coil of wire wound on a soft iron core forming an electromagnet. A
current is passed through the coil in the direction indicated by the arrows. Mark the N and
S poles produced in the iron core.
Answer. Using clock face rule
A is South pole. B is North pole.
Q.20. If the circular coil has n turns, the field produced is n times as large as that produced by a
single turn. Justify it.
Answer. This is because the current in each circular turn has the same direction, and the field due
to each turn then just adds up along the axis of the coil
Q.21. Name any two appliances which are based on the application of heating effect of electric
current.
Answer. Room heater and geyser.