Electric Current

Electric current is the rate of flow of electric charge through the cross-section of a conductor when a potential difference is applied across its ends.

• The flow of charge is mainly due to the movement of electrons.
• The SI unit of electric current is the ampere (A).

Below diagram shows how current and electrons flow and how the battery works.

Types Of Electric Current

• Direct Current (DC): The flow of electric charge is in one constant direction (e.g., batteries).
• Alternating Current (AC): The flow of electric charge periodically reverses direction (e.g., household power grids).
• Current flows through conductors, such as copper wires, due to the presence of free-moving electrons in the material.
• Electric current powers devices, appliances, and systems in homes, industries, and technology.
• The flow of current can be influenced by factors like resistance, temperature, and the material of the conductor.

Classification of Materials Based on Electrical Conductivity

Conductor:

• A conductor is a material that allows electric charge to flow through it easily.
• Conductors have free electrons that can move easily, facilitating the flow of electric current.
• Common conductors include metals such as copper, aluminum, and silver.
• Properties of conductors are: Low resistance to the flow of electric current, High electrical conductivity, Used in electrical wiring and circuits.

Did You Know?

The best conductor of electricity is Silver.

Insulator:

• An insulator is a material that resists the flow of electric current.
• Insulators have very few free electrons, which makes it difficult for electric charges to move through them.
• Common insulators include rubber, plastic, wood, glass, and ceramics.
• Some Properties of insulators are High resistance to electric current, Low electrical conductivity, and use to protect or separate conductors to prevent electric shocks or short circuits.

Unit of Electric Current

• Electric current is measured as charge flowing per second; its SI unit is ampere (A), where 1 A = 1 coulomb/second.
• One ampere is the current when 6.241 × 10¹⁸ electrons pass through a conductor in one second.
• Smaller currents are measured in milliampere (mA = 10^⁻³ A) and microampere (μA = 10^{⁻⁶ A).}

Electric Current Formula

The electric current can be represented as the rate of flow of electric charge (q), which mathematically can be represented as.

Where:

• I = Electric Current
• Q = Electric Charge
• T = Time

Conventional Current Flow Vs Electron Flow

Conventional Current Flow

Conventional current flow refers to the direction in which positive charge is considered to flow in an electrical circuit. By convention, current is assumed to flow from the positive terminal to the negative terminal of a power source, even though, in reality, electrons (which are negatively charged) flow in the opposite direction, from the negative terminal to the positive terminal.

Electron Flow

Electron flow refers to the actual movement of electrons in a conductor, which flows from the negative terminal to the positive terminal of a power source. Since electrons carry a negative charge, they are attracted to the positive terminal and repelled by the negative terminal, resulting in this direction of flow. Electron flow is the opposite of conventional current flow, which assumes positive charge flows from the positive to the negative terminal.

The differences between conventional current flow and electron flow:

Electric Current Effects

1. Chemical Effect of Electric Current

When Electric current is passed through a medium that is conducting in nature, the solution breaks into its respective ions, and effects are seen visibly. The major effects that are prominent,

• The color of the solution may change.
• The deposition of metal at the electrodes may be seen.
• There can be the formation of gas bubbles at the electrodes.

2. Magnetic Effect of Electric Current

Electric current is the motion of electrons. Stationary charges produce an electric field, but moving charges generate a magnetic field. When a current-carrying wire is placed near a metallic needle, the needle gets deflected due to the magnetic field produced by the current. A major application of this magnetic effect is the creation of electromagnets, which are formed by passing current through a coil of wire.

Biot-Savart Law states that Magnetic Field (B) can be created by electric currents (i):

where:

• μ₀​ = permeability of free space
• I = current
• dl = current element vector
• r = distance from element to observation point
• r = unit vector from current element to the point
• × = cross product

3. Heating Effect of Electric Current

When current flows through a conductor, heat energy is produced due to the resistance of the conductor. A higher resistance restricts the flow of current, and the electrical energy of the blocked current is converted into heat. This phenomenon is called the heating effect of current. The heat energy produced is given by the formula.

H = I²RT

Where,

• H is Heat energy released
• Current is flowing in the conductor
• R is Resistance offered by the conductor
• T is Time for which the current was flowing in the conductor

Solved Problems

Question 1: In a conductor, 10 Coulombs of charge flow for 5 seconds; determine the current produced.

Solution The current in a circuit is given by,

I = q/t

⇒ I = 10/5 Amperes

⇒ I = 2 Amperes

Therefore, 2 amperes of current flows in the circuit.

Question 2: In the circuit given below, Find the current flowing through the circuit.

Solution In the figure provided, it is clear that there are two resistances, and they are in series.

R = R₁ + R₂ ⇒ R = 2+ 2 ⇒ R = 4 ohms

From Ohms Law,

V = IR ⇒ I = V/R ⇒ I = 20/4

⇒ I = 5 Amperes 

Question 3: What is the Heat energy produced when 2 amperes of current are flowing in a circuit for 5 seconds having an overall resistance in the circuit of 4 ohms?

Solution: Heat Energy Produced is given by,

H = I² × R × t

⇒ H = (2)²×4 × 5

⇒ H = 16 × 5

⇒ H = 80 Joules

Therefore, 80 Joules heat is produced in the circuit.

Question 4: What is the heat energy produced when 3 amperes of current are flowing in a circuit for 10 seconds with an overall resistance of 6 ohms?

Solution: The formula to calculate heat energy is given by:

H = I² × R × t

Substitute the given values:

I = 3 A, R = 6 Ω, t = 10 s

⇒ H = (3)² × 6 × 10

⇒ H = 9 × 6 × 10

⇒ H = 540 joules

The heat energy produced is 540 joules.

Question 5: A conductor carries a current such that 3 × 10²⁰ electrons pass through it in 4 minutes. Calculate the current flowing through the conductor.

Solution: Total charge

Q = n × e

Q = (3 × 10²⁰ ) × (1.6 × 10^-19 )

Q = 4.8 × 10¹

Q = 48 C

Time,
4 minutes = 4 × 60 = 240

I = 0.2 A

Unsolved Problems

Question 1: A current of 2.5 A flows through a conductor for 12 seconds. Find the total charge passing through the conductor.

Question 2: A 10 Ω resistor is connected to a 50 V battery. Calculate Current in the circuit and Heat produced in 4 s.

Question 3: Two resistors of 5 Ω and 7 Ω are connected in series across 24 V. Find total resistance, current in the circuit and Voltage drop across each resistor

Question 4: Two resistors of 6 Ω and 12 Ω are connected in parallel to a 24 V battery. Find equivalent resistance, total current, and current through each resistor.

Question 5: A circuit contains a 4 Ω and 8 Ω resistor connected in series, and this combination is connected in parallel with a 6 Ω resistor to a 12 V source. Find equivalent resistance of the circuit, total current from the battery, and current through the 6 Ω resistor

Related Articles

• Ohm's Law
• Heating effect of electric current
• Biot-Savart Law
• Magnetic field on the circular axis current carrying loop