EASY
JEE Main/Advance
IMPORTANT
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Intensity of magnetic field of the earth at a point inside a hollow iron box is :

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Important Questions on Magnetic Effect of Current

MEDIUM
JEE Main/Advance
IMPORTANT
When a piece of a ferromagnetic substance is put in a uniform magnetic field, the flux density inside it is four times the flux density away from the piece. The magnetic permeability of the material is
EASY
JEE Main/Advance
IMPORTANT
The relative permeability of air is: 
HARD
JEE Main/Advance
IMPORTANT
A thin rectangular magnet, suspended freely, has a period of oscillation equal to T. Now, it is broken into two equal halves (each having half of the original length) and one piece is made to oscillate freely in the same field. If it's period of oscillation is T', then the ratio TT' is
MEDIUM
JEE Main/Advance
IMPORTANT
A galvanometer has a resistance of 20 Ω and reads full-scale when 0.2 V is applied across it. To convert it into a 10 A ammeter, the galvanometer coil should have a 
EASY
JEE Main/Advance
IMPORTANT
A galvanometer coil has a resistance 90 Ω and full scale deflection current 10 mA. A 910 Ω resistance is connected in series with the galvanometer to make a voltmeter. If the least count of the voltmeter is 0.1 V, the number of divisions on its scale is
EASY
JEE Main/Advance
IMPORTANT

A and B are two concentric circular conductors of centre O and carrying current i1 and i2 as shown in the diagram. If ratio of their radii 1:2 and ratio of the flux densities at O due to A and B is 1:3 then the value of i1i2 will be-

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JEE Main/Advance
IMPORTANT

Two thick wires and two thin wires, all of the same materials and same length form a square in the three different ways P, Q and R as shown in fig with current direction shown, the magnetic field at the centre of the square is zero in case

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EASY
JEE Main/Advance
IMPORTANT
A long straight wire carries a current along the x-axis. Consider the points A0,1,0, B0,1,1, C1,0,1 and D1,1,1. Which of the following pairs of points will have magnetic fields of the same magnitude-