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

• $\frac{\mathrm{R}}{4}$

• $\frac{\mathrm{R}}{16}$

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

The equivalent resistance across A and B is     

• 2 Ω

• 3 Ω

• 4 Ω

• 5 Ω

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

• $\frac{\mathrm{B}}{6}$

• $\frac{\mathrm{B}}{4}$

• $\frac{\mathrm{B}}{3}$

• $\frac{\mathrm{B}}{2}$

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

• $\frac{\mathrm{r}}{4}$

• $\frac{\mathrm{r}}{2}$

• 2r

• 4r

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

27.

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 $\mathrm{\varphi } = 5{\mathrm{t}}^3 - 100 \mathrm{t} + 300$. 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

• 0^o

• 30^o

• 45^o

• 60^o