Oxidation of the filament in a light bulb is prevented by the introduction of
- A. hydrogen
- B. oxygen
- C. argon
- D. mercury vapour
an electron moves with a speed of 2.0 x 106ms-1 in a straight line. Calculate the wave length of the electron wave. [mass of an electron = 9.1 x 10-31 kg][Planck’s constant = 6.6 x 10-34Js]
- A. 3.63 x 10-19m
- B. 6.51 x 10-9m
- C. 4.24 x 10-8m
- D. 7.25 x 10-8m
Eddy currents can be reduced by
- A. using coil of high resistance
- B. winding the coil on a soft iron core
- C. creating holes in the metal plates
- D. using coil of low resistance
The resonant frequency of an a.c circuit is 1000 kHz. If each of the capacitance and inductance in the circuit is reduced by 50%, and no other changes are made, the resonant frequency will become
- A. 250kHz
- B. 750kHz
- C. 1000kHz
- D. 2000kHz
The energy, E stored in an inductor of inductance L when current I passes through it is given by the equation
- A. E = \(\frac{1}{2} LI^2\)
- B. E = LI2
- C. E \(\frac{1}{2}LI\)
- D. E = \(\frac{1}{2} L^2I\)
In order to prevent bar magnets from losing their strength, they are stored wih keepers such that the two bars are placed with
- A. like poles facing each other and the keepers placed between them
- B. like poles facing each other and the keepers placed between them
- C. unlike poles facing each other and the keepers placed at their ends
- D. unlike poles facing each other and the keepers placed between them
Which of the following factors will increase the sensitivity of moving coil meter?
- A. strong spring
- B. low numbers of turns
- C. small area of coil
- D. soft iron core
Which of the following factors does not affect the electric resistance of wire?
- A. length
- B. mass
- C. temperature
- D. cross-sectional area
In the wiring of houses, the fuse is connected to the wire coloured
- A. blue
- B. brown
- C. yellow
- D. yellow and green
A galvanometer of internal resistance 50\(\Omega\) and full scale deflection of 20 mA is converted into a voltmeter by connecting a resistor of resistance 1950\(\Omega\) in series to it. Calculate the maximum voltage that can be read by the voltmeter
- A. 20V
- B. 30V
- C. 38V
- D. 40V
Determine the potential difference. V across the parallel resistors
- A. 2.0V
- B. 2.3V
- C. 3.0V
- D. 0.7V
Use the diagram above to calculate the current, I.
- A. 0.60A
- B. 0.97A
- C. 1.03A
- D. 5.00A
Capacitors are used in the following devices, except
- A. water pumping machines
- B. ceiling fans
- C. electric irons
- D. television sets
A positively charged glass rod is placed near the cap of a positively charged electroscope. The divergence of the leaf is observed to
- A. decrease
- B. increase
- C. remain the same
- D. increase and collapse immediately
As the air column of length L in an air pipe decreases, the frequency of the sationary wave emitted
- A. decreases
- B. increases
- C. varies as L2
- D. varies as \(\sqrt{L}\)
The amplitude of a sound wave determines its
- A. frequency
- B. quality
- C. loudness
- D. pitch
Which of the following electromagnetic wave has the longest wavelength?
- A. radio-waves
- B. gamma rays
- C. infrared waves
- D. ultraviolet rays
A lens that is thinner at the middle and thicher at the edges is
- A. diverging
- B. converging
- C. plano-convex
- D. converging meniscus
A ray of light travels from air to water. The refeactive index of water is given by the expression
- A. \(\frac{\text{velocity in water}}{\text{velocity in air}}\)
- B. \(\frac{\text{sine of angle of refraction}}{\text{sine of angle of incidence}}\)
- C. \(\frac{\text{apparent depth}}{\text{real depth }}\)
- D. \(\frac{\text{wavelength in air}}{\text{wavelength in water}}\)
From the diagram, the correct equation for the refractive index n of the medium is
- A. n = tan i
- B. n = \(\frac{sin i}{sin 90^o}\)
- C. n = \(\frac{sin i}{cos (90^o - i)}\)
- D. n = sin 90oC
When an object is placed at the principal focus of a concave mirror, the location of the image formed is
- A. between principal focus and pole
- B. between principal focus and centre of curvature
- C. at infinity
- D. at centre of curvature