Physics

Free set

Showing 101 to 125 of 1648 questions (page 5 of 66).

101. In a step up transformer

A. the secondary has fewer turns than the primary B. the secondary voltage is lower C. the secondary current is greater D. the secondary has more turns than the primary E. power in the secondary exceeds that in the primary

102. Eddy currents in transformer cores are reduced by

A. using a solid iron core B. laminating the core C. increasing the frequency D. using a copper core E. removing the core

103. The root mean square value of an alternating current of peak value I_0 is

A. I_0 B. I_0/2 C. I_0/sqrt(2) D. sqrt(2) I_0 E. 2 I_0 / pi

104. The resonant frequency of a series LC circuit is

A. 2 pi sqrt(LC) B. 1/(2 pi sqrt(LC)) C. sqrt(LC) D. 1/(2 pi LC) E. 2 pi LC

105. The capacitive reactance of a capacitor

A. increases with frequency B. decreases with frequency C. is independent of frequency D. is zero at all frequencies E. equals the resistance

106. In a purely inductive AC circuit, the current

A. leads the voltage by 90 degrees B. lags the voltage by 90 degrees C. is in phase with the voltage D. leads by 45 degrees E. is zero

107. The speed of electromagnetic waves in free space is

A. 3 x 10^6 m s-1 B. 3 x 10^8 m s-1 C. 3 x 10^10 m s-1 D. 1.5 x 10^8 m s-1 E. 332 m s-1

108. The power factor of a purely resistive AC circuit is

B. 0.5 C. 0.707 D. 1 E. infinite

109. The SI unit of Young's modulus is

A. N m B. N m-1 C. N m-2 D. N m2 E. dimensionless

110. A solid in which the atoms have no long range order is called

A. crystalline B. amorphous C. polymeric D. ferromagnetic E. isomorphic

111. In an insulator, the energy gap between the valence and conduction bands is

A. zero B. about 0.7 eV C. about 1.1 eV D. greater than about 5 eV E. negative

112. Above the Curie temperature, a ferromagnetic material becomes

A. diamagnetic B. paramagnetic C. superconducting D. more strongly ferromagnetic E. non-magnetic in the sense of losing all response

113. Stress within the elastic limit is

A. independent of strain B. directly proportional to strain C. inversely proportional to strain D. proportional to the square of strain E. zero

114. A p-n junction diode conducts appreciably when

A. reverse biased B. forward biased C. unbiased D. at absolute zero E. the depletion region widens

115. The output ripple frequency of a full wave rectifier fed from a 50 Hz supply is

A. 25 Hz B. 50 Hz C. 100 Hz D. 150 Hz E. zero

116. A Zener diode in a voltage regulator circuit is operated in

A. forward bias B. reverse bias beyond the breakdown voltage C. zero bias D. the saturation region E. the cut off region

117. Which logic gate is called a universal gate?

A. AND B. OR C. NOT D. NAND E. XOR

118. In an ideal operational amplifier, the input impedance and open loop gain are respectively

A. zero and zero B. infinite and infinite C. infinite and zero D. zero and infinite E. finite and unity

119. For a transistor operating as an amplifier, the emitter base junction and collector base junction are

A. both forward biased B. both reverse biased C. forward and reverse biased respectively D. reverse and forward biased respectively E. unbiased

120. Doping silicon with a pentavalent impurity produces

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

121. According to the special theory of relativity, the speed of light in free space is

A. different for different observers B. the same for all inertial observers C. dependent on the source velocity D. dependent on the observer velocity E. infinite

122. In the photoelectric effect, the maximum kinetic energy of the emitted electrons is

A. hf B. hf + work function C. hf - work function D. work function - hf E. independent of frequency

123. The de Broglie wavelength of a particle of momentum p is

A. hp B. h/p C. p/h D. h/p2 E. h p2

124. The Compton effect demonstrates the

A. wave nature of light B. particle nature of light C. transverse nature of light D. polarization of X-rays E. interference of X-rays

125. Heisenberg's uncertainty principle states that the product of the uncertainties in position and momentum is

A. zero B. at least of the order of h/(4 pi) C. at most h D. equal to hf E. independent of h

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