CBSE
A material ‘B’ has twice the specific resistance of ‘A’. A circular wire made of ‘B’ has twice the diameter of a wire made of ‘A’. Then for the two wires to have the same resistance, the ratio
2
1
1/4
1/2
A.
2
In a series resonant LCR circuit, the voltage across R is 100 volts and R = 1 kΩ with C = 2µF. The resonant frequency ω is 200 rad/s. At resonance the voltage across L is
4 × 10−3 V
2.5 × 10^{−2} V
40 V
250 V
D.
250 V
In a Wheatstone’s bridge, there resistances P, Q and R connected in the three arms and the fourth arm is formed by two resistances S_{1} and S_{2} connected in parallel. The condition for bridge to be balanced will be
A.
Needles N_{1}, N_{2} and N_{3} are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will
attract all three of them
attract N_{1} and N_{2} strongly but repel N_{3}
attract N_{1} strongly, N_{2} weakly and repel N_{3} weakly
attract N_{1} strongly, but repel N_{2} and N_{3} weakly
C.
attract N_{1} strongly, N_{2} weakly and repel N_{3} weakly
Two rigid boxes containing different ideal gases are placed on a table. Box A contains one mole of nitrogen at temperature T_{0}, while Box B contains one mole of helium at temperature (7/3) T_{0}. The boxes are then put into thermal contact with each other and heat flows between them until the gases reach a common final temperature. (Ignore the heat capacity of boxes). Then, the final temperature of the gases, T_{f}, in terms of T_{0} is
D.
The current I drawn from the 5 volt source will be
0.17 A
0.33 A
0.5 A
0.67 A
C.
0.5 A
In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a
circle
helix
straight line
ellipse
C.
straight line
An electric dipole is placed at an angle of 30° to a non-uniform electric field. The dipole will experience
a torque only
a translational force only in the direction of the field
a translational force only in a direction normal to the direction of the field
a torque as well as a translational force
D.
a torque as well as a translational force
Two insulating plates are both uniformly charged in such a way that the potential difference between them is V_{2} −V_{1} = 20 V. (i.e. plate 2 is at a higher potential). The plates are separated by d = 0.1 m and can be treated as infinitely large. An electron is released from rest on the inner surface of plate 1. What is its speed when it hits plate 2?
(e = 1.6 × 10^{−19} C, me = 9.11 × 10^{−31} kg)
32 × 10^{−19} m/s
2.65 × 10^{6} m/s
7.02 × 10^{12} m/s
1.87 × 10^{6} m/s
B.
2.65 × 10^{6} m/s
The Kirchhoff’s first law (∑ i= 0) and second law (∑iR = ∑E), where the symbols have their usual meanings, are respectively based on
conservation of charge, conservation of energy
conservation of charge, conservation of momentum
conservation of energy, conservation of charge
conservation of momentum, conservation of charge
A.
conservation of charge, conservation of energy
Kirchhoff's Ist law or KCl states that the algebraic sum of current meeting at any junction is equal to zero. Thus, no charge has been accumulated at any junction i.e., the charge is conserved, and hence KCl is based on conservation of charge.