Top electrical interview questions and answers about electrical basics

Electrical basics:

Voltage :

The unit is volt. voltage is the amount of potential energy between two points on a circuit. One point has more charge than another. This difference in charge between the two points is called voltage.

Resistance:

The unit is ohm. It is represented by two circuits with equal voltages and different resistances. The circuit with the higher resistance will allow less charge to flow, meaning the circuit with higher resistance has less current flowing through it.

Current:

The unit is ampere. It measure the amount of charge flowing through the circuit over a period of time

Power:

The unit is watt. Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. It is the rate of doing work.

Volt-ampere (VA) :

Volt-ampere is the unit used for the apparent power in an electrical circuit. The apparent power equals the product of root mean square voltage and root mean square current. In direct current circuits, this product is equal to the real power in watts.

Kilovolt Ampere:

One kilovolt ampere (KVA)  is equal to 1000 volt amperes

Power Factor :

Ratio of watts to volt amperes

Capacitance:

Capacitance is the ratio of the amount of electric charge stored on a conductor to a difference in electric potential. There are two closely related notions of capacitance: self capacitance and mutual capacitance. 

Conductor:

Conductor is an object or type of material that allows the flow of charge in one or more directions. Materials made of metal are common electrical conductors. 

Insulator:

Electrical insulator is a material that does not easily allow flow of electricity through an electric current. Materials typically used to insulate include rubber, plastic and glass. In transformers and electric motors, varnish is used.

Most important Formulas:

Voltage V = I × R = P / I = √(P × R) in volts V         

Current I = V / R = P / V = √(P / R) in amperes A

Resistance R = V / I = P / I^2 = V^2 / P in ohms Ω    

Power P = V × I = R × I^2 = V^2 / R in watts 

Electric voltage : Ohm's Law

V = IR

V = P / I     

V = (P*R)/2

Electric Current : Ohm's Law

I = V / R         

I = P / V         

I = (P / R)1/2       

Electric Resistance : Ohm's Law

R = V / I         

R = V^2/ P         

R = P / I^2     

Electric Power

P = V I        

P = R I^2     

P = V^2/ R        

where, 

P = power (watts, W)

V = voltage (volts, V)

I = current (amperes, A)

 R = resistance (ohms, Ω)

Electric Energy :

Electric energy is power multiplied time. 

W = P t     

where, 

W = energy (Ws, J)

t = time (s) 

Electrical Motor :

Electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force in the form of torque applied on the motor's shaft.

Electrical transformer:

The transformer is a static machine used for transforming power from one circuit to another without changing frquency.

Transformer operates on ac supply. The transformer working on the principle of an mutual induction.

It doesn't have rotating or moving parts so transformer is a static machine.