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Showing 2026 to 2050 of 3046 questions (page 82 of 122).

2026. SONAR is used to determine the depth of the sea using

A. ultrasonic waves and their echo time B. infrasonic waves only C. visible light D. gamma rays E. radio waves

2027. The principle of superposition states that where two waves meet, the resultant displacement is

A. the product of the individual displacements B. the algebraic sum of the individual displacements C. always zero D. the larger of the two displacements E. the difference of the amplitudes only

2028. If the tension in a stretched string is made four times, the fundamental frequency becomes

A. half B. one quarter C. double D. four times E. unchanged

2029. Diffraction effects are most noticeable when the size of the obstacle or aperture is

A. equal to the amplitude B. much smaller than the wavelength in every dimension C. much larger than the wavelength D. independent of the wavelength E. comparable to the wavelength

2030. In a diffraction grating with more lines per centimetre, the diffracted orders become

A. independent of wavelength B. more widely separated C. less intense only D. identical to interference fringes E. closer together

2031. A magnifying glass produces an image that is

A. always at the focus B. real and inverted C. virtual, erect and magnified D. real and diminished E. virtual and diminished

2032. A telescope is said to be in normal adjustment when the final image is formed

A. at infinity B. at the objective C. at the focal point of the objective D. at the near point E. on the retina directly

2033. A spectrometer is used to

A. measure current B. magnify small objects C. measure resistance D. detect magnetic fields E. disperse light and measure wavelengths

2034. The entropy of a substance during melting at its melting point

A. becomes zero B. remains constant C. decreases D. increases E. becomes negative

2035. A diesel engine is generally more efficient than a petrol engine because it operates with a

A. lower peak temperature B. higher compression ratio C. spark plug D. richer fuel mixture E. lower compression ratio

2036. An ideal gas is compressed adiabatically. Its temperature

A. becomes zero B. stays constant C. falls D. first rises then falls E. rises

2037. Heat supplied to a gas at constant pressure is used to

A. increase the internal energy and do external work B. increase the pressure only C. do external work only D. increase the internal energy only E. lower the temperature

2038. The electric flux through a surface of area A held at angle theta to a uniform field E is

A. E/A cos theta B. EA sin theta C. EA tan theta D. EA E. EA cos theta

2039. Charge on an irregularly shaped conductor accumulates most densely

A. inside the conductor B. at flat regions C. at sharply curved regions and points D. at the centre of mass E. uniformly everywhere

2040. The potential energy of two point charges q1 and q2 separated by r is

A. k q1 divided by q2 r B. k q1 q2 divided by r C. k q1 q2 times r D. k q1 q2 divided by r squared E. zero

2041. In a cathode ray tube, electrons are produced by

A. field ionization of the gas B. photoelectric emission from the anode C. secondary emission at the screen D. radioactive decay E. thermionic emission from a heated filament

2042. A 100 W bulb operated for 10 hours consumes

A. 10 kWh B. 1 kWh C. 100 kWh D. 0.1 kWh E. 1000 kWh

2043. The resistance of a metallic conductor at temperature t is related to its resistance at 0 degrees Celsius by

A. R = R0 alpha t B. R = R0 divided by alpha t C. R = R0 (1 + alpha t) D. R = R0 (1 - alpha t) E. R = alpha t

2044. A cell of emf 2 V and internal resistance 0.5 ohm delivers current to a 1.5 ohm external resistor. The current is

A. 1 A B. 1.33 A C. 4 A D. 0.5 A E. 2 A

2045. Kirchhoff's second rule is based on the conservation of

A. momentum B. charge C. flux D. mass E. energy

2046. Magnetic flux density is defined as the

A. flux times area B. flux per unit area perpendicular to the field C. force per unit charge D. flux per unit length E. current per unit area

2047. A mass spectrometer separates ions according to their

A. speed only B. temperature C. mass to charge ratio D. chemical reactivity E. colour

2048. The magnetic dipole moment of a coil of N turns, area A, carrying current I is

A. N I A squared B. I A divided by N C. N I divided by A D. N I A E. N A divided by I

2049. Thomson's experiment on the deflection of cathode rays determined the

A. charge to mass ratio of the electron B. Planck constant C. radius of the atom D. mass of the proton E. charge of the electron

2050. A DC generator differs from an AC generator in that it uses

A. no coil B. slip rings C. a split ring commutator D. no magnet E. a capacitor

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