When a nucleus is formed by bringing protons and neutrons together, the actual mass of the formed nucleus is less than the sum of the masses of the energy equivalent of this mass difference is the
- A. lost energy
- B. work function
- C. binding energy
- D. stability energy
The major difference between a pure semiconductor and a pure metal is that
- A. metals are harder than semiconductor
- B. while resistance of metals decrease with temperature , the reverse is the case for semiconductor
- C. the resistance of metals increases with temperature, while for semiconductors, it is the reverse
- D. metals have forbidden gaps while semiconductors have not
In a semi conductor junction diode, as the depletion or barrier layer is forward-biased, the layer
- A. widens
- B. narrows
- C. remains constant
- D. widens then narrows
When an alternating current given by I = 10sin (120π)t passes through a 12Ω resistor, the power dissipated in the resistor is
- A. 1200W
- B. 600W
- C. 120W
- D. 30W
The maximum kinetic energy of the photoelectron emitted from a metal surface is 0.34eV. If the work function of the metal surface is 1.83eV,find the stopping potential.
- A. 2.17V
- B. 1.49V
- C. 1.09V
- D. 0.34V
The force on a charge moving with velocity v in a magnetic field B is half of the maximum force when the angle between v and B is
- A. 90o
- B. 45o
- C. 30o
- D. 0o
A circuit has an area of 0.4m2 and consists of 50 loops of wire. If the loops are twisted and allowed to rotate at a constant angular velocity of 10 rad s-1 in a uniform magnetic field of 0.4T, the amplitude of the induced voltage is
- A. 8V
- B. 16V
- C. 20V
- D. 80V
The count rate of a radioactive material is 800 count/min. If the half-life of the material is 4 days, what would the count rate be in 16 days later
- A. 200 count / min
- B. 100 count / min
- C. 50 count / min
- D. 25 count / min
A ray incident on a glass prism undergoes minimum deviation when the
- A. incident angle is equal to the angle of refraction
- B. refraction angle equals 90o
- C. incident angle equals 90o
- D. incident angle is equal to the angle of emergence
The most suitable cell used for short interval switches in electric bells is a
- A. lead- acid accumulator
- B. Daniel cell
- C. Leclanche cell
- D. nickel iron accumulator
Which of the following pairs of light rays show the widest separation in the spectrum of white light
- A. Blue and red
- B. Green and yellow
- C. Indigo and violet
- D. Orange and red
I It retains its magnetic much longer than steel.
II It is more easily magnetized than steel
III It is more easily demagnetized than steel
IV It produces a stronger magnet than steel
Which combination of the above makes iron preferable to steel in the making of electromagnets?
- A. I and II only
- B. II and III only
- C. I, III, and IV only
- D. II, III and IV only
A magnetic field is said to exist at a point if a force is
- A. exerted on a stationary charge at the point
- B. exerted on a moving charge at the point
- C. deflected at the point
- D. strengthened at the point
An electron of charge 1.6 x 10-19C is accelerated between two metal plates. If the kinetics energy of the electron is 4.8 x 10-17J, the potential difference between the plate is
- A. 30V
- B. 40V
- C. 300V
- D. 400V
A wire of 5Ω resistance is drawn out so that its new length is two times the original length. If the resistivity of the wire remains the same and the cross-sectional area is halved, the new resistance is
- A. 40Ω
- B. 20Ω
- C. 10Ω
- D. 5Ω
I the diagram above, what would happen to the current I, if another resistor, R2, is connected in parallel to R1?
- A. It will increase because the equivalent resistance will increase
- B. It will decrease if R2 is greater than R1
- C. It will increase because the effective resistance will decrease
- D. It will decrease if R2 is less than R1
The operation of an optical fibre is based on the principal of
- A. dispersion of light
- B. interference of light
- C. refraction of light
- D. polarization of light
In the diagram above, if each of the resistors can dissipate a maximum of 18W without becoming excessively heated, what is the maximum power the circuit can dissipate?
- A. 27W
- B. 18W
- C. 9W
- D. 5W
A positive charged rod X is brought near as uncharged metal sphere Y and is then touched by a finger with X still in place. When the finger is removed, the result is that y has
- A. no charge and a zero potential
- B. a positive charge and zero potential
- C. a negative charge and positive potential
- D. a negative charge and a negative potential
If 1.2 x 10^6J of heat energy is given off in 1 sec from a vessel maintained at a temperature gradient of 30Km-1, the surface area of the vessel is
[ thermal conductivity of the vessel = 400Wm-1K-1]
- A. 1.0 x 102m2
- B. 9. 0 x 102m2
- C. 1.0 x 103m2
- D. 9.0 x 104m2
A 2000W electric heater is used to heat a metal object of mass 5kg initially at 10oC. If a temperature rise of 30oC is obtained after 10min, the heat capacity of the material is
- A. 6.0 x 104JoC-1
- B. 4.0 x 104JoC-1
- C. 1.2 x 104JoC-1
- D. 8.0 x 103JoC-1