Basic Electrical Quantities

To understand the electrical concept it is necessary to know about current, voltage, power, and energy. First, it is necessary what is the SI unit of the different parameters.

The SI unit of the parameter is shown below.

Parameter	Unit
1. Current	A
2. Voltage	Volt
3. Power	Watt
4. Energy	Joule

Electric Current:

• It is defined as the flow of electrons.
• Suppose you throw a ball, and the ball flows in projectile motion, here ball can be assumed as an electron which is to flow, and the direction toward the ball comes to motion is assumed as Current.
• Current is also called the flow of the electric charge carrier.
• It flows from positive direction to negative direction.

Mathematically current is given by (relation with charge and time),
i = q/t,

i is current q, is electric charge in and t is time in sec, Hence unit of current is coulomb/sec, which is called an Ampere.

DEFINITION OF 1 AMPERE:

It is defined as when 1 Coulomb (6.25×10¹⁸ ) charge passes in 1-second.

Current Source Symbol:

VOLTAGE:

Voltage is the electrical force that causes current to flow.

It is also called as an Electromotive force(EMF) or Potential difference.

RESISTANCE:

• The property of a material which opposes the flow of current through the material itself is called its resistance.
• The opposition exists because of the fact that moving electrons which constitute current do not have a clear path to move.

Electrical POWER and ENERGY:

• According to physics "Ability/ Tendency to do work is called energy and how fast work is done is called power.
• The relation between power and energy is; ENERGY = POWER × TIME
• In terms of electrical engineering, a unit of POWER is Watt and a unit of ENERGY is kWh
• In terms of DC circuits Power is the product of VOLTAGE & CURRENT.
• There are 3 types of power in the case of electrical:

• Active Power
• Reactive Power
• Apparent Power

MCQs on Basic Electrical Concepts

Q1: What is the SI unit of electric current?

A. Volt

B. Watt

C. Ampere

D. Coulomb

Answer: C. Ampere

Q2: How is electric current defined?

A. Flow of protons

B. Flow of neutrons

C. Flow of electrons

D. Flow of photons

Answer: C. Flow of electrons

Q3: What is the mathematical formula for electric current?

A. $i = v/r$
B. $i = q/t$
C. $i = r/v$
D. $i = q^2 \times t$
Answer: B. $i=q\mathrm{/}t$

Q4: One ampere of current is defined as the flow of how much charge in one second?

A. 6.25×10⁶ electrons
B. $6.25 \times 10^{18}$electrons
C. $6.25 \times 10^{12}$electrons
D. $1 \times 10^{3}$electrons
Answer: B. $6.25 \times 10^{18}$electrons

Q5: What is the SI unit of voltage?

A. Joule

B. Coulomb

C. Volt

D. Watt

Answer: C. Volt

Q6: What is another term used for voltage?

A. Potential resistance

B. Electromotive force (EMF)

C. Conductance force

D. Electrical impedance

Answer: B. Electromotive force (EMF)

Q7: Which property of a material opposes the flow of electric current?

A. Conductance

B. Capacitance

C. Resistance

D. Reactance

Answer: C. Resistance

Q8: What is the relationship between power and energy?

A. Power = Energy × Time

B. Energy = Power × Time

C. Power = Energy / Time

D. Energy = Time / Power

Answer: B. Energy = Power × Time

Q9: What is the unit of electrical energy in commercial terms?

A. Watt

B. Volt

C. kWh

D. Ampere

Answer: C. kWh

Q10: In a DC circuit, power is given by the product of which two parameters?

A. Voltage and Resistance

B. Voltage and Current

C. Current and Resistance

D. Voltage and Capacitance

Answer: B. Voltage and Current

Q11: Which type of power is used to perform actual work in an electrical circuit?

A. Reactive Power

B. Apparent Power

C. Active Power

D. Complex Power

Answer: C. Active Power

Q12: What is the SI unit of power?

A. Volt

B. Watt

C. Ohm

D. Joule

Answer: B. Watt

Q13: What does a current source symbol represent in a circuit?

A. A source of voltage

B. A source of constant current

C. A resistor in series

D. A capacitor in parallel

Answer: B. A source of constant current

Q14: What is reactive power in an electrical circuit?

A. Power used for actual work

B. Power stored and released by reactive components

C. Total power supplied to the circuit

D. Power wasted in resistance

Answer: B. Power stored and released by reactive components