Engineering Physics II Practice Test 8

1. From the figure, what is β_ac when V_CE is 10V and I_c is 4 mA?

100

150

200

2. How is persistent current produced in supermagnets?

By increasing the resistance

By passing ac current

By magnetising it

By passing dc current

3. In a circuit the load current is 5 mA and the unregulated output is 10 V. If the voltage drop across the Zener diode is 3 V, what should be the value of resistance?

150 Ω

50 Ω

100 Ω

125 Ω

4. A semiconducting crystal 12mm long, 5mm wide and 1mm thick has a magnetic flux density of 0.5Wb/m² applied from front to back perpendicular to largest faces. When a current of 20mA flows length wise through the specimen, the voltage measured across its width is found to be 37μV. What is the Hall coefficient of this semiconductor?

3.7×10^-6 m³/C

37×10^-6 m³/C

3.7×10⁶ m³/C

5. The Knee Voltage for germanium is _________

0.7 V

1.4 V

0.1 V

0.3 V

6. The conductivity of germanium at 20°C is 2/ohm m. What is its conductivity at 40°C? E_g=0.72eV

1.38×10^-23/Ohm m

293/Ohm m

1.0002/Ohm m

313/Ohm m

7. The following graph depicts the I-V characteristics of which instrument?

Zener diode

Photodiode

Solar Cell

Light Emitting Diode

8. The resistance of the semiconductor decreases in forward biased.

False

True

9. What is the energy level below which all levels are completely occupied at Zero Kelvin called?

Boson Energy

Fermi Energy

Ground Energy

Stable Energy

10. In a semiconductor it is observed that three-quarters of the current is carried by electrons and one quarters by holes. If the drift speed is three times that of the holes, what is the ratio of electrons to holes?

1 : 2

2 : 1

1 : 1

4 : 1