10 Question-Answer on Magnetic effects of current
1. A moving charge will produce
(a) No field
(b) An electric field
(c) A magnetic field
(d) Both ‘b’ and ‘c’
Ans: ( d)
2. Magnetic field induction B due to current I at all points on the axis of element is
(a) Zero
(b) Maximum
(c) Minimum
(d) Either ‘b’ or ‘c’
Ans: ( a)
3. A current is passed through a straight wire. The magnetic field established around it has its lines of forces
(a) Elliptical
(b) Circular
(c) Oval
(d) Parabolic
Ans: ( b)
4. A circular coil A of radius r carries current I. another circular coil B of radius 2r carries current of I. the magnetic fields at the centres of the circular coils are in the ratio of:
(a) 3 : 1
(b) 4 : 1
(c) 1 : 1
(d) 2 : 1
Ans: (d)
5. If we double the radius of a current carrying coil keeping the current unchanged, the magnetic field at its centre will:
(a) remain unchanged
(b) become double
(c) be halved
(d) become four times
Ans: ( c)
6. A current carrying power line carries current from west to east. The direction of magnetic field 1 m above the power line will be:
(a) East to west
(b) West to east
(c) South to north
(d) North to south
Ans: (d)
7. The strength of the magnetic field around an infinite current carrying conductor is:
(a) Same every where
(b) Directly proportional to distance
(c) inversely proportional to distance
(d) inversely proportional to the square of the distance
Ans: (c)
8. the magnetic dipole moment of current loop is independent of
(a) number of turns
(b) area of loop
(c) current in the loop
(d) Magnetic field in which it is lying.
Ans: (d)
9. When a straight conductor is carrying an electric current.
(a) There are circular magnetic lines of force around it.
(b) There are no magnetic lines of force near it.
(c) There are magnetic lines of force parallel to conductor along the direction of current.
(d) There are magnetic lines of force opposite to conductor along the direction of current.
Ans: ( a)
10. A current is flowing north along a power line. The direction of the magnetic field above it, neglecting the earth’s field is towards:
(a) North
(b) East
(c) South
(d) West.
Ans: (b)