1. From the following list of devices, choose the device that only turns-on for a fixed-value of anode-cathode voltage
a) PUT
b) SCR
c) SUS
d) BJT
Explanation: Unlike the other devices the SUS only turns-on for a fixed value of anode to cathode voltage.
2. The SCS (Silicon Controlled Switch) is a
a) two terminal device
b) three terminal device
c) four terminal device
d) five terminal device
Explanation: The SCS is a four terminal device A,K,KG & AG.
3. The SCS is a four layer, four terminal thyristor. Can be turned on by
a) the anode gate
b) the cathode gate
c) either of the gates
d) gating both the gates together
Explanation: The SCS has two gates, anode-gate and cathode-gate. Either of the gates could be used to turn on the device.
4. The SCS (Silicon Controlled Switch) can be turned on by two methods, by applying __________ and __________
a) positive pulse to the anode gate, positive pulse to the cathode gate
b) positive pulse to the anode gate, negative pulse to the cathode gate
c) negative pulse to the anode gate, positive pulse to the cathode gate
d) negative pulse to the anode gate, negative pulse to the cathode gate
Explanation: Either of the gates could be used to turn on the device.
5. Which of the following devices provide complete isolation between triggering circuit and power circuit?
a) PUT
b) LASCR
c) SUS
d) DIAC
Explanation: Complete Isolation between triggering circuit & power circuit is the major advantage of using LASCR as they are light activated or light trigged.
6. The DIAC can be represented by
a) two SCRs in anti-parallel
b) two SCRs in parallel
c) two diodes in anti-parallel
d) two diodes in parallel
Explanation: The DIAC is nothing but a bi-directional diode.
7. The TRIAC can be represented by
a) two SCRs in anti-parallel
b) two SCRs in parallel
c) two diodes in anti-parallel
d) two diodes in parallel
Explanation: The TRIAC is a bidirectional SCR.
8. The GTO (gate turn-off thyristor) is a
a) p-n-p-n device
b) p-n-p device
c) p-metal-n device
d) p-n single junction device
Explanation: Just like a SCR, the GTO is a four layer p-n-p-n device.
9. The GTO can be turned off
a) by a positive gate pulse
b) by a negative gate pulse
c) by a negative anode-cathode voltage
d) by removing the gate pulse
Explanation: The GTO can be turned off by applying a negative gate pulse to the gate terminal.
10. The anode current is ideally limited by the
a) gate pulse amplitude
b) internal impedance of the device
c) load Impedance
d) gate circuit impedance
Explanation: The SCR or any device is connected through the load, hence the magnitude of the anode current (same as load current) will depend on the supply voltage and load impedance.