Physics

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Showing 1251 to 1275 of 1648 questions (page 51 of 66).

1251. The SI unit of self inductance is

A. tesla B. henry C. farad D. ohm E. weber

1252. The energy stored in an inductor of inductance L carrying current I is

A. L/I2 B. LI2 C. LI D. (1/2)LI E. (1/2)LI2

1253. In a step up transformer

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

1254. Eddy currents in transformer cores are reduced by

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

1255. The root mean square value of an alternating current of peak value I_0 is

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

1256. The resonant frequency of a series LC circuit is

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

1257. The capacitive reactance of a capacitor

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

1258. In a purely inductive AC circuit, the current

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

1259. The speed of electromagnetic waves in free space is

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

1260. The power factor of a purely resistive AC circuit is

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

1261. The SI unit of Young's modulus is

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

1262. A solid in which the atoms have no long range order is called

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

1263. In an insulator, the energy gap between the valence and conduction bands is

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

1264. Above the Curie temperature, a ferromagnetic material becomes

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

1265. Stress within the elastic limit is

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

1266. A p-n junction diode conducts appreciably when

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

1267. The output ripple frequency of a full wave rectifier fed from a 50 Hz supply is

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

1268. A Zener diode in a voltage regulator circuit is operated in

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

1269. Which logic gate is called a universal gate?

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

1270. In an ideal operational amplifier, the input impedance and open loop gain are respectively

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

1271. For a transistor operating as an amplifier, the emitter base junction and collector base junction are

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

1272. Doping silicon with a pentavalent impurity produces

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

1273. According to the special theory of relativity, the speed of light in free space is

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

1274. In the photoelectric effect, the maximum kinetic energy of the emitted electrons is

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

1275. The de Broglie wavelength of a particle of momentum p is

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

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