Vipra ShrivastavaSenior Manager - Content
Electricity exists in two forms, Alternating Current (AC) and Direct Current (DC). The fundamental difference between AC and DC is that direct current travels only in one specific direction, whereas alternating current reverses its direction from time to time. A circuit is called an alternating current circuit when its source differs from time to time.
Differences Between AC and DC
| Alternating Current |
Direct Current |
|---|---|
| An alternating current is appropriate for travel over longer distances like inter-cities and inter-states. It is safe and can maintain electric power over long distances. |
Direct current is not suitable for transfer power over longer distances. It loses electric power. |
| The electrons in alternating current keep shuffling their direction - back and forth. |
The electrons in DC move only in one direction. |
| Generally, the frequency of AC is 50 Hz or 60 Hz. It depends on the country. |
DC has zero frequency. |
| AC generators use an electromagnet. |
DC generators use a permanent magnet. |
| AC generators possess slip rings. |
DC generators contain a commutator. |
| The cause of the bidirectional flow of electrons is the rotating coil in a magnetic field that is uniform within a stationary coil. |
The unidirectional flow is due to the constant magnetic field. |
| The power factor is between 0 and 1. |
The power factor is always 1. |
| A load of AC is inductive, resistive, and capacitive. |
The load in DC is usually resistive. |
Difference Between AC and DC in Class 12
The topic forms part of the fourth unit of Class 12 Physics - Electromagnetic Induction and Alternating Currents. The unit is expected to carry 17 marks approximately.
Illustrated Examples of Differences Between AC and DC
Example 1) If a resistor of 100 is connected to a 220 V, 50 Hz alternating current supply, answer the following:
- What is the net power utilized over a full cycle?
- What is the current’s RMS value circuit?
Solutions:
- The net power utilized can be ascertained by the following formula:
P = VI
= 220 x 2.2
= 484 W
2. The RMS value of the alternating current in the circuit can be found by:
I = V / R
I = 220 / 100
I = 2.20 A
Example 2)
(a) The highest voltage of the alternating current supply is 300 V. Find the RMS voltage of the same?
(b) The value of RMS in an alternating circuit current is 10 A. Find the peak current of the circuit?
Solution:
- The peak voltage of the alternating current supply, V0 = 300V
RMS voltage can be ascertained by the following:
V = V0 / 2
V = 300 /2
V = 212.1 V
2. RMS value of the current can be found by
I0 = 2I
= 102
= 14.1 A
Example 3) Ascertain the resonant frequency of a series of LCR circuit where
- L = 2.0 H
- C = 32 F
- R = 10
Find the Q-value of the given circuit?
Solution:
Given,
L = 2.0 H (Inductance)
C = 32 F (Capacitance)
R = 10 (Resistance)
The resonant frequency can be found as shown below
r = 1 / LC
= 1 / 2*32*10-6
= 1 / 8*10-3
= 125 s-1
The circuit’s Q-value can be determined by
1/R *L/C
= 1/102/32*10-6
= 1/10 * 1 / 4 * 10-3
= 25
Hence, the Q-value of the circuit is 25.
FAQs on Difference Between AC and DC
Q: A 44 mH inductor is connected to 220 V, 50 Hz ac supply. Determine the rms value of the current in the circuit.
A: Inductance of the Inductor, L = 44 mH = 44 × 10−3 H
Supply voltage, V = 220 V
Supply frequency, ? = 50 Hz
Angular frequency, ? = 2??
Inductive reactance, ?L = ? = 2??L
rms value of current is given as
I = ?/?L
= 220 / 2?×50×44 ×10−3 = 15.92 A
Hence, the rms value of the current in the circuit is 15.92 A
Q: A 60 μF capacitor is connected to a 110 V, 60 Hz ac supply. Determine the rms value of the current in the circuit.
A: Capacitance of the capacitor, C = 60 ?F = 60 × 10−6 F
Supply voltage, V = 110 V
Supply frequency, ? = 60 Hz
Angular frequency, ? = 2??
Capacitive reactance, ?? = 1 / ?C = 1 / 2??C
rms value of current is given by I = ? / ??
= 110 × 2 × ? × 60 × 60 × 10−6 = 2.49 A
Hence, the rms value of current is 2.49 A
Q: In above two questions, what is the net power absorbed by each circuit over a complete cycle. Explain your answer.
A: In the inductive circuit:
rms value of current, I = 15.92 A
rms value of voltage, V = 220 V
The net power absorbed can be obtained by
P = VI cos ∅ , where ∅ is the phase difference between alternating voltage and current = 90°
So P = VI cos 90° = 0
In the capacitive circuit:
rms value of current, I = 2.49 A
rms value of voltage, V = 110 V
The net power absorbed can be obtained by
P = VI cos ∅ , where ∅ is the phase difference between alternating voltage and current = 90°
So P = VI cos 90° = 0
Q: What type of electricity does a battery have, AC and DC?
A: All the batteries, including lithium-ion batteries used in powering electric equipment like drones, computers, etc., function on direct current. DC can be stored in a battery, unlike AC.
Q: What is the main difference between AC and DC?
A: The primary distinction between AC and DC is the direction of flow in which the current travels.
Q: Which is comparatively more fatal: AC or DC?
A: AC (alternating current) is at least five times more fatal than DC (direct current). The primary cause for this severe effect on the human body is the frequency of the alternating current. A frequency of 60 cycles is quite harmful. A small voltage of 25 volts, in this frequency, can prove fatal.
Q: What type of current is used in households?
A: An alternating current is used in households.
Q: What is the primary advantage of direct current electricity?
A: The most prominent upside of direct current electricity is that it is easier to store than alternating current electricity.
News & Updates
Physics Current Electricity Exam
Student Forum
Anything you would want to ask experts?Popular Courses After 12th
Exams: BHU UET | KUK Entrance Exam | JMI Entrance Exam
Bachelor of Design in Animation (BDes)
Exams: UCEED | NIFT Entrance Exam | NID Entrance Exam
BA LLB (Bachelor of Arts + Bachelor of Laws)
Exams: CLAT | AILET | LSAT India
Bachelor of Journalism & Mass Communication (BJMC)
Exams: LUACMAT | SRMHCAT | GD Goenka Test