A uniform wire of resistance R and length L is cut into four equal parts, each of length L/4, which are then connected in parallel combination. The effective resistance of the combination will be
R
4 R
A capacitor of capacitance 5µF is connected as shown in the figure. The internal resistance of the cell is 0.5 Ω . The amount of charge on the capacitor plates is
80 μC
40 μC
20 μC
10 μC
An electric current passes through a long straight copper wire. At a distance 5 cm from the straight wire, the magnetic field is B. The magnetic field at 20 cm from the straight wire would be
An electron of mass m and charge q is travelling with a speed v along a circular path of radius r at right angles to a uniform magnetic field B. If speed of the electron is doubled and the magnetic field is halved, then resulting path would have a radius of
2r
4r
D.
4r
In a perpendicular magnetic field
Magnetic force = centripetal force
Bqv =
⇒ r =
∴
⇒
A galvanometer acting as a voltmeter should have
low resistance in series with its coil
low resistance in parallel with its coil
high resistance in series with its coil
high resistance in parallel with its coil
A frog can be levitated in magnetic field produced by a current in a vertical solenoid placed below the frog. This is possible because the body of the frog behaves as
paramagnetic
diamagnetic
ferromagnetic
anti-ferromagnetic
The magnetic flux linked with a coil at any instant t is given by the equation . The magitude of emf induced in coil after 3 s is
10 V
20 V
35 V
70 V
In 0.1 s, the current in a coil increases from 1 A to 1.5A. If inductance of coil is 60 mH, then induced current in external resistance of 32 will be
1 A
0.5 A
0.2 A
0.1 A
In a series L-C-R circuit, resistance R = 10 Ω and the impedance Z = 10 Ω. The phase difference between the current and the voltage is
0o
30o
45o
60o