The fundamental frequency in an open organ pipe is equal to the third harmonic of a closed organ pipe. If the length of the closed organ pipe is 20 cm, the length of the open organ pipe is
13.2 cm
8 cm
16 cm
12.5 cm
The efficiency of an ideal heat engine working between the freezing point and boiling point of water, is
26.8%
20%
12.5%
6.25%
An electron falls from rest through a vertical distance h in a uniform and vertically upward directed electric field E. The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is
Smaller
5 times greater
Equal
10 times greater
The electrostatic force between the metal plates of an isolated parallel plate capacitor C having a charge Q and area A, is
Independent of the distance between the plates
Linearly proportional to the distance between the plates
Inversely proportional to the distance between the plates
Proportional to the square root of the distance between the plates
Current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage applied) is 20 div/V. The resistance of the galvanometer is
40 Ω
25 Ω
500 Ω
250 Ω
A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from
The current source
The magnetic field
The induced electric field due to the changing magnetic field
The lattice structure of the material of the rod
An inductor 20 mH, a capacitor 100 µF and a resistor 50 Ω are connected in series across a source of emf, V = 10 sin 314 t. The power loss in the circuit is
0.79 W
0.43
1.13
2.74 W
A metallic rod of mass per unit length 0.5 kg m–1 is lying horizontally on a smooth inclined plane which makes an angle of 30° with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction 0.25 T is acting on it in the vertical direction. The current flowing in the rod to keep it stationary is
7.14 A
5.98 A
11.32 A
14.76 A
A carbon resistor of (47 ± 4.7) kΩ is to be marked with rings of different colours for its identification. The colour code sequence will be
Violet – Yellow – Orange – Silver
Yellow – Violet – Orange – Silver
Green – Orange – Violet – Gold
Yellow – Green – Violet – Gold
A set of 'n' equal resistors, of value 'R' each, are connected in series to a battery of emf 'E' and internal resistance 'R'. The current drawn is I. Now, the 'n' resistors are connected in parallel to the same battery. Then the current drawn from battery becomes 10 I. The value of 'n' is
10
11
9
20
A.
10
In series grouping equivalent resistance Rseries = nR
In parallel grouping equivalent resistance Rparallel = R/n