Physics

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Showing 226 to 250 of 1648 questions (page 10 of 66).

226. A Wheatstone bridge is balanced when

A. R1 R2 = R3 R4 B. R1/R2 = R3/R4 C. R1 + R2 = R3 + R4 D. R1 R3 = R2 R4 E. the galvanometer reads maximum

227. The resistance of a thermistor with a negative temperature coefficient

A. increases with temperature B. decreases with temperature C. is independent of temperature D. becomes zero at 0 K E. varies linearly with current

228. Maximum power is delivered by a cell of emf E and internal resistance r to an external resistance R when

A. R = 0 B. R = r C. R = 2r D. R is infinite E. R = r/2

229. The specific resistance of a conductor depends on

A. its length B. its area of cross section C. its shape D. the nature of the material and temperature E. the current through it

230. Two resistances of 6 ohm and 3 ohm are connected in parallel. The equivalent resistance is

A. 9 ohm B. 4.5 ohm C. 2 ohm D. 18 ohm E. 3 ohm

231. The force on a charge q moving with velocity v at angle theta to a magnetic field B is

A. qvB cos theta B. qvB sin theta C. qvB tan theta D. qv/B E. qB/v

232. The magnetic field inside a long solenoid with n turns per unit length carrying current I is

A. mu_0 I B. mu_0 n I C. mu_0 I / n D. mu_0 n / I E. n I / mu_0

233. The SI unit of magnetic flux is

A. tesla B. weber C. henry D. gauss E. ampere turn

234. A charged particle moving parallel to a uniform magnetic field experiences a force of

A. maximum magnitude B. half the maximum C. zero D. qvB E. qE

235. Ampere's circuital law relates the line integral of the magnetic field around a closed loop to

A. the enclosed charge B. the enclosed current C. the flux through the loop D. the emf induced E. the loop area

236. Lenz's law is a consequence of the conservation of

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

237. The motional emf induced in a rod of length l moving with velocity v perpendicular to a magnetic field B is

A. Bvl B. Bv/l C. B/vl D. Bl/v E. B2vl

238. The SI unit of self inductance is

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

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

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

240. 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

241. 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

242. 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

243. 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

244. 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

245. 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

246. 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

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

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

248. The SI unit of Young's modulus is

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

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

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

250. 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

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