The primary coil of a transformer has N turns and is connected to a 120 V a.c. power line. If the secondary coils has 1 000 turns and a terminal voltage of 1 200 volts, what is the value of N?
- A. 120
- B. 100
- C. 1 000
- D. 1 200
The current through a resistor in an a.c circuit is given as 2 sin wt. Determine the d.c. equivalent of the current
- A. \(\frac{1A}{\sqrt{2}}\)
- B. \(\sqrt{2}\)A
- C. 2 A
- D. 2\(\sqrt{2}\)A
I. Low pressure.
II. High pressure.
III. High p.d.
IV. Low p.d.
Which combination of the above is true of the conduction of electricity through gases?
- A. I and IV only
- B. I and III only
- C. II and IV only
- D. II and III only
The particles emitted when \( ^{39}_{19}K \text{ decay to } ^{39}_{19}K \) is
- A. gamma
- B. beta
- C. electron
- D. alpha
A cell can supply current of 0.4 A and 0.2 A through a 4.0Ω and 10.0Ω resistors respectively.
This internal resistance of the cell is
- A. 2.0Ω
- B. 1.0Ω
- C. 2.5Ω
- D. 1.5Ω
The ratio of electrostatic force F\(_E\) to gravitational force F\(_G\) between two protons each of charge e and mass m, at a distance d is
- A. \(\frac{e}{4πε_oGm}\)
- B. \(\frac{e^2}{Gm^2}\)
- C. \(\frac{Gm^2}{4πε_oe^2}\)
- D. \(\frac{e^2}{4πε_oGm^2}\)
when a piece of rectangular glass block is inserted between two parallel capacitor,at constant plate area and distance of separation, the capacitance of the capacitor will
- A. increase
- B. decrease
- C. decrease then increase
- D. remain constant
In a Daniel cell, the depolarizer, positive and negative electrodes are respectively
- A. copper sulphate, copper and zinc
- B. manganese dioxide, carbon and zinc
- C. sulphuric acid, lead oxide and lead
- D. potassium hydroxide, nickel and iron.
The cost of running five 60 W lamps and four 100 W lamps for 20 hours if electrical energy cost #10.00 per kwh is
- A. 280.00
- B. 160.00
- C. 120.00
- D. 140.00
A working electric motor takes a current of 1.5 A when the p.d across it is 250V. If its efficiency is 80%, the power output is
- A. 300.0W
- B. 469.0W
- C. 133.0W
- D. 4.8W
A student is at a height 4m above the ground during a thunderstorm. Given that the potential difference between the thundercloud and the ground is 10\(^7\)V, the electric field created by the storm is
- A. \(2.0\times 10^6 NC^{-1}\)
- B. \(2.5\times 10^6 NC^{-1}\)
- C. \(1.0\times 10^7 NC^{-1}\)
- D. \(4.0\times 10^7 NC^{-1}\)
A resistance R is connected across the terminal of an electric cell of internal resistance 2Ω and the voltage was reduced to 3/5 of its nominal value.
The value of R is
- A. 3 Ω
- B. 2 Ω
- C. 1 Ω
- D. 6 Ω
A cell of internal resistance r supplies current to a 6.0Ω resistor and its efficiency is 75%. Find the value of r.
- A. 4.5Ω
- B. 1.0Ω
- C. 8.0Ω
- D. 2.0Ω
A gas with initial volume of 2 X 10\(^{-6}m^3\) is allowed to expand to six times its initial value at constant pressure of 2 x 10\(^5Nm^{-2}\). The work done is?
- A. 2.0J
- B. 4. 0 J
- C. 12.0 J
- D. 2.4 J
A string is fastened tightly between two walls 24cm apart. The wavelength of the second overtone is
- A. 24cm
- B. 16cm
- C. 12cm
- D. 8cm
A plane sound wave of frequency 85.5Hz and velocity 342ms-1 is reflected from a vertical wall. At what distance from the wall does the wave have antinode?
- A. 2m
- B. 4m
- C. 1m
- D. 3m
The thermometric substance of an absolute thermometer is
- A. alcohol
- B. mercury
- C. helium
- D. platinum
The pressure of a given mass of a gas changes from 300Nm\(^{-2}\) to 120Nm\(^{-2}\) while the temperature drops from 127°C to -73°C. The ratio of the final volume to the initial volume is
- A. 2 : 5
- B. 5 : 4
- C. 4 : 5
- D. 5 : 2
The driving mirror of a car has a radius of curvature of 1m. A vehicle behind the car is 4m from the mirror. Find the image distance behind the mirror.
- A. 8/7
- B. 4/9
- C. 9/2
- D. 4/7
The terrestrial telescope has one extra lens more than the astronomical telescope. The extra lens is for
- A. improving the sharpness
- B. creating an inverted image
- C. magnification of the image
- D. erection of the image
A ray of light strikes a plane mirror at an angle of incidence of 35°. If the mirror is rotated through 10°, through what angle is the reflected ray rotated?
- A. 70°
- B. 45°
- C. 25°
- D. 20°