17) What is the least count of a Vernier calliper if 9 divisions of the main scale is equal to 10 divisions on the Vernier scale and each division in the main scale is 1mm?

18) Which of the following makes use of ferro resonance?

19) What is the use of an emitter follower circuit?

20) Given, 1/3 + 1/4 + x = 7/12. What is the value of x ?

21) How many select inputs are required for a 8:1 multiplexer?