Alternating Current
The ratio of peak value and r.m.s value of an alternating current is
√2
Two streams of protons move parallel to each other in the same direction. They will
if the length of a conductor wire is doubled its conductance will be
1/4 of the original value
the direction of the electric field at a point is the direction of force on this type of test charge
Positive Test Charge
A bar magnet is dropped along the axis of a coper ring held horizontally. The acceleration of fall is
Less than g
An electric bulb marked as 50W- 200V is connected across a 100V supple. The present power of the bulb is?
12.5V
To increase the current sensitivity of a moving coil galvanometer by 50%, its resistance becomes twice its initial resistance. By what factor does the voltage sensitivity change
Decreases by 25%
In a closed circuit the current I (in ampere) at an instance of time t (in seconds) is given by I=4-0.08t the number of electrons flowing in 50 seconds through the cross section of the conductor is
6.25 x 1020
Two charges of 2μC and -3μC are separated by a distance of 0.5m In air find the magnitude of the force between them.
0.216N
The phenomenon that limits the rise of current in a RL circuit when the circuit is first closed
Self-Inductance
In an AC circuit the reactance of a coil is times its resistance, the phase difference between the voltage across the coil to the current through the coil will be
𝝅/3
A galvanometer of resistance 50Ω gives a full scale deflection fr a current 5 x 10-4 A. the resistance that should be connected in series with the galvanometer to read 3V is?
5950Ω
If the electric current in a lamp decreases by 5% then the power output decreases by
10%
2 Charged spherical conductors of radius R1 and R2 are connected by a wire then the ratio of the surface charge densities of the spheres is
In an AC generator, if the number of turns of the coil is doubled while keeping angular velocity and magnetic flux density constant, by what factor does the peak induced emf change?
2
An alternating emf e=220√2 sin 100t V isappied to a capacitor 1F the current flowing through the capacitor is?
22mA
A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the center of the loop is B. It is then bent into a circular coil of n turns. The magnetic field at the center of this coil of n turns will be
n2B
A storage battery of emf 8.0v and internal resistance of 0.5 ohm is being charged by a 120v DC supply using a series resistor of 15.5 ohm what is the terminal voltage of the battery during charging
11.5V
Two copper balls each weighing 10 grams are kept in air 10cm apart if one electron from every 106 atoms is transferred from one ball to the other the coulomb force between them is ( atomic weight of copper 63.5g)
2.0x108N
An average induced e.m.f of 1V appears in a coil when the current in it is change from 10A in one direction to 10A in opposite direction in 0.5sec. Self-Inductance of the coil is?
25mH
A coil has an inductance of 0.7 henry and is joined in series with a resistance of 220Ω. When the alternating emf of 220V at 50Hz is applied to it then the phase through which current lags behind the applied emf will be
45o
Two 10cm long straight wires each carrying a current of 5A are kept parallel to each other. If each wire experienced a force of 10-5N then separation between the wires is
5cm
The resistance of a platinum wire at 0oC is 2Ω and 6.8Ω at 80oC. The temperature coefficient of resistance of the wire is?
3x10-2C-1
Two electric dipoles of moment p and 27p are placed in opposite directions on a line at a distance of 10cm the electric field will be 0 at point between the dipoles of moment p is?
2.5cm
A long solenoid has 1000 turns. When a current of 4wA flows through it, the magnetic flux linked with each turn of the solenoid is 4x10-3 Wb. The self-inductance of the solenoid is
1