Polytechnic Electronics and Electrical Engineering 3

Question 1

What is the impedance of a pure inductor with inductance L at angular frequency ω?

Accepted Answer

Z = ωL

Answer

The inductive reactance (impedance of a pure inductor) is XL = ωL, where ω = 2πf.

Question 2

A transformer has 200 primary turns and 50 secondary turns. If the primary voltage is 240V, what is the secondary voltage?

Accepted Answer

60V

Answer

Using V2/V1 = N2/N1: V2 = 240 × (50/200) = 60V (step-down transformer).

Question 3

What is the function of a rectifier circuit in power supplies?

Accepted Answer

Converts AC to DC

Answer

A rectifier converts AC (alternating current) to DC (direct current) using diodes to allow only one polarity.

Question 4

In Boolean algebra, what is the result of A + Ā (A OR NOT-A)?

Accepted Answer

1

Answer

A OR NOT-A always equals 1 (TRUE) because either A or its complement must be true — this is the complement law.

Question 5

What is the power dissipated by a 10Ω resistor carrying 2 amperes of current?

Accepted Answer

40W

Answer

Using P = I²R = (2)² × 10 = 4 × 10 = 40W.

Polytechnic Practice Test