## Tuesday, July 10, 2012

### CBSE PHYSICS X: Magnetic Effect of current Solve Practice questions

Q. What do you understand by magnetic effect of electric current?
Ans: The phenomenon due to which, a wire behaves like a magnet when electric current is passed through it, is called as the magnetic effect of electric current.
Q. What is magnetic field?
Ans: The region around the magnet, where force of attraction or repulsion can be felt by magnetic materials, is called as magnetic field.
Q. Why does a compass needle get deflected when brought near a bar magnet ?
Ans: The magnet exerts its influence in the region surrounding it.So, the compass needle shows deflection when brought near a magnet or an electromagnet.
Q. Why two magnetic field lines do not intersect each other?
Ans: The magnetic field lines the magnetic field lines form closed curves and originate in fix direction inside and out side magnet so magnetic field lines do not intersect each other.
Q. What happens to the deflection of the compass needle placed at a given point if the current in the straight copper wire is changed?
Ans: The deflection in the needle changes.if the current is increased, the deflection also increases. B µ I
Q. What happens to the deflection of the needle if the compass is moved from the straight copper wire but the current through the wire remains the same?
Ans: The deflection in the needle decreases. Thus the magnetic field produced by the given current in the conductor decreases as the distance from it increases. B µ 1/r
Q. Explain Maxwell's right hand thumb rule?
Ans: According to Maxwell's right hand thumb rule,
“If we hold the current-carrying conductor in our right hand in such a way that the thumb is stretched along the direction of the current, then the curled fingers give the direction of the magnetic field produced by the current”,
Q. What are the properties of magnetic field due to a current through a straight wire?
Ans The properties of magnetic field due to a current through a straight wire are:
1. The magnitude of the magnetic field produced at a given point increases as the current through the wire increases.
2. The magnetic field produced by a given current in the conductor decreases as the distance from it increases.
3. The concentric circles representing the magnetic field around a current-carrying straight wire become larger and larger as we move away from it.
4. If the direction of the current is reversed in the wire, the lines will still be circular, but the directions of the lines will be reversed, which can be verified using the compass needle.
Q. Give characteristics of magnetic field lines.
Ans: (i) They represent the magnetic field.
(ii) They are directed from north to South Pole outside a magnet and from south to North Pole inside a magnet.
(iii) The field lines are closed curves.
(iv) The strength of magnetic field in a region is determined by closeness of the field lines in that region.
(v) The closer the field lines are, greater will be the field strength and vice–versa.
(vi) No two field lines ever cross each other as it would mean two different directions of field at point of intersection, which is not possible.
(viii) The parallel lines represent the uniform magnetic field whereas converging lines or diverging lines represents the non uniform magnetic field.
Q. Give the factors that affect strength of magnetic field at a point due to a straight conductor carrying current.
Ans : Magnitude of electric current, perpendicular distance between that point and conductor.
Q. A current-carrying straight conductor is placed in the east-west direction. What will be the direction of the force experienced by this conductor due to earth’s magnetic field? How will this force get affected on? (a) reversing the direction of floe of current (b) doubling the magnitude of current.Ans .The direction of earth’s magnetic field is from G-south to G-north. Let current is from west to east. Therefore force is vertically upwards.
(a) By reversing the direction of current, the direction of will be reversed i.e.vertically downwards.
(b) The magnitude of the force is doubled.
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