# PHYSICS : MAGNETIC EFFECTS OF CURRENT Online Test

A long wire carries a steady current. It is bent into a circle of one turn and the magnetic field at the centre of the coil is B. It is then bent into a circular loop of n turns. The magnetic field at the centre of the coil is ____.
nB
n2B
2nB
2n2B
Two wires of same length are shaped into a square and a circle. If they carry same current, ratio of the magnetic moment is ____.
2 : (
( : 2
( : 4
4 : (
A wire carrying current I and other carrying 2I in the same direction produces a magnetic field B at the mid point. What is the field when 2I wire is switched off?
B / 2
2B
B
4B
When the current flowing in a circular coil is doubled and the number of turns of the coil in it is halved, the magnetic field at its centre becomes ____.
Four times
Same
Half
Double
PQRS is a square loop made of uniform conducting wire the current enters the loop at P and leaves at S. Then the magnetic field is ____.
Maximum at the centre of the loop
Zero at the centre of loop
Zero at all points inside the loop
Zero at all points outside of the loop
The current in the windings on a toroid is 2.0A. There are 400 turns and the mean circumferential length is 40cm. If the inside magnetic field is 1.0T, the relative permeability is near to ____.
100
200
300
400
A long straight wire carrying current of 30A is placed in an external uniform magnetic field of induction 4 ( 10–4T. The magnetic field is acting parallel to the direction of current. The magnitude of the resultant magnetic induction in tesla at a point 2.0 cm away from the wire is ____.
10–4
3 ( 10–4
5 ( 10–4
6 ( 10–4
The earth's magnetic induction at a certain point is  This is to be annulled by the magnetic induction at the centre of a circular conducting loop of radius 5 cm. The required current in the loop is ____.
0.56 A
5.6 A
0.28 A
2.8 A
A straight wire of diameter 0.5 mm carrying a current of 1 A is replaced by another wire of 1 mm diameter carrying the same current. The strength of magnetic field far away is ____.
Twice the earlier value
Half of the earlier value
Quarter of its earlier value
Unchanged
/
Description:

Questions are mainly from various aspects of magnetic effect of current like Ampere's circuital law, solenoid etc

Discussion

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2639 days 8 hours 40 minutes ago

explanations should be given to questions.
in the 4rth question i'm getting answer as half but the answer says same. if u make the number of turns of a coil half of its original value then it's radius should get doubled the original value .

3868 days 1 hours 36 minutes ago

Kajal Sengupta
Physics 9th to 12 th grade,CIE, Edexcel, AP, IB , CBSE, ICSE
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