281.  In general, materials which are good thermal conductors are
A. difficult to produce
B. good electric conductors
C. poor electric conductors
D. good semiconductors

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282.  A heat sink will dissipate heat more rapidly if
A. its temperature is the same as the temperature of the surrounding air.
B. its surface area is increased.
C. it is covered with a material having a high thermal resistance
D. it iskept away from air currents.

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283.  In the common-emitter circuit, the dc bias arrangment that gives the most stable conditions is
A. Base current bias
B. Self-bias
C. Base voltage bias
D. Fixed bias

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284. In common-emitter circuit with base voltage bias, the improved stability is due to
A. the use of a single supply battery.
B. the use of negative feedback.
C. the combination of fixed base voltage and a series smitterresistance.
D. the fact that the circuit has a high current gain

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285.  Compared to fixed bias, self-bias in a common-emitter amplifier
A. produces a greater voltage amplification
B. produces a more stable operation
C. tends to overheat the transistor
D. requires an extra bias supply

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286. The collector voltage in a normally biased common-emitter transistor is equal to the
A. voltage drop across the collector load resistor
B. collector bias supply voltage
C. collector bias supply voltage less the voltage drop across the load resistor
D. collector bias supply voltage plus the voltage drop across the load resistor

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287. For linear amplification, the dc operating point should beset
A. near cutoff
B. anywhere on the collector load line
C. midway between cutoffand saturation
D. near saturation

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