Mixed Practice

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Showing 1876 to 1900 of 3046 questions (page 76 of 122).

1876. The relation between electric field intensity and potential is

A. E = V/r2 B. V = E r2 C. E = V r D. E = -dV/dr E. E = dV/dr times r2

1877. Two resistors of 4 ohm and 6 ohm are joined in series across a 20 V supply. The current is

A. 0.5 A B. 10 A C. 2 A D. 5 A E. 1.2 A

1878. An ideal ammeter and an ideal voltmeter have respectively

A. infinite and zero resistance B. zero and infinite resistance C. equal finite resistances D. zero and zero resistance E. infinite and infinite resistance

1879. A galvanometer is converted into an ammeter by connecting

A. an inductor in series B. a high resistance in series C. a diode in parallel D. a capacitor in series E. a low resistance in parallel

1880. The heat produced in a resistor is given by

A. I2Rt B. I2R/t C. IRt2 D. IR2t E. IRt

1881. The resistance of a conductor of length L, area of cross section A and resistivity rho is

A. rho A / L B. L / rho A C. A / rho L D. rho L / A E. rho L A

1882. In the resistor colour code, the fourth band indicates

A. the multiplier B. the power rating C. the first digit D. the tolerance E. the temperature coefficient

1883. The magnetic field at a perpendicular distance r from a long straight wire carrying current I is

A. mu_0 I r B. mu_0 I / (2 pi r) C. mu_0 I / (2r) D. mu_0 I / r2 E. 2 pi mu_0 I r

1884. The force on a 2 m length of wire carrying 3 A placed perpendicular to a 0.5 T field is

A. 0.75 N B. 6 N C. 3 N D. 12 N E. 1.5 N

1885. A loudspeaker converts electrical energy into sound using

A. electrostatic attraction B. piezoelectric heating only C. the photoelectric effect D. thermal expansion E. the force on a current carrying coil in a magnetic field

1886. A diamagnetic substance in a magnetic field is

A. weakly repelled B. weakly attracted C. strongly attracted D. permanently magnetized E. unaffected

1887. Flux linkage through a coil of N turns each enclosing flux Phi is

A. N/Phi B. N Phi C. N2 Phi D. Phi/N E. Phi

1888. A generator converts

A. heat to electrical energy B. electrical energy to mechanical energy C. chemical to electrical energy D. mechanical energy to electrical energy E. light to electrical energy

1889. Self induction in a coil always

A. opposes the change in current B. reverses the current C. stops the current D. assists the change in current E. increases the resistance

1890. A transformer with 500 primary turns and 2500 secondary turns supplying 220 V to the primary gives a secondary voltage of

A. 44 V B. 550 V C. 220 V D. 2500 V E. 1100 V

1891. The peak to peak value of an alternating voltage of peak value V0 is

A. V0/sqrt(2) B. V0/2 C. V0 sqrt(2) D. 2V0 E. V0

1892. A radio receiver is tuned to a station by adjusting the

A. capacitance of the tuning circuit B. resistance in the circuit C. loudspeaker impedance D. aerial length only E. supply voltage

1893. Electrical power is transmitted at high voltage over long distances in order to

A. avoid using transformers B. reduce the voltage at the consumer end directly C. increase the current D. increase the resistance of the line E. reduce the current and hence the I squared R loss

1894. The bulk modulus of a material relates

A. stress to temperature B. strain to time C. volume stress to volume strain D. shear stress to shear strain E. tensile stress to longitudinal strain

1895. A material that can be drawn into thin wires is described as

A. ductile B. amorphous C. malleable D. elastic only E. brittle

1896. Doping a semiconductor with a trivalent impurity produces

A. an insulator B. a conductor C. an intrinsic semiconductor D. a p-type semiconductor E. an n-type semiconductor

1897. In a metallic conductor, the valence and conduction bands

A. are both completely full B. overlap or the valence band is partly filled C. have a gap of 1.1 eV D. are both completely empty E. are widely separated

1898. The region near a p-n junction that is free of mobile charge carriers is called the

A. conduction band B. depletion region C. potential well D. channel E. forbidden gap

1899. The peak inverse voltage of a diode is the maximum reverse voltage it can withstand

A. without breaking down B. while conducting C. in forward bias D. during rectification only in a bridge circuit E. at zero current

1900. A bridge rectifier uses

A. a centre tapped transformer and one diode B. three diodes C. two diodes D. one diode E. four diodes

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