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Electric Circuit

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Key Points: Electric Circuit

Maharashtra State Board: Class 8

Concept of Electric Circuit

An electric circuit is a setup that allows electric current to flow through connected components, making devices work, like lighting up a bulb.

Components of the Circuit:

Cell holder: This holds the dry cells (batteries) that provide the energy needed for the current.
Electric bulb: lights up when current flows through it.
Plug key: acts like a switch that can open or close the circuit.
Wires: Connect all the components, allowing the current to travel through them.

Working

Closing the plug key completes the circuit after fitting the dry cell in the cell holder (Fig. a) and connecting the components as shown in Fig. b.
Once the plug key is closed, electric current flows from the cell through the wires to the bulb, making it light up.
The circuit breaks if you remove the cell or open the plug key. This stops the current, and the bulb goes off.

(a) Cell holder

(b) Simple electric circuit

Maharashtra State Board: Class 9

Circuit Diagram

An electric circuit is a continuous path that allows electric current to flow. It consists of conducting wires, a cell (or battery), and other components like resistors, all connected in a loop. Electric circuits study or utilise the current flow, measure electrical quantities such as current and voltage, and regulate the operation of electrical devices. A circuit diagram shows the arrangement of components in a circuit. And it uses special symbols to represent components like resistors, batteries, wires, ammeters, and voltmeters.

Electrical Circuit

Maharashtra State Board: Class 10

Experiment

1. Aim: To study the transfer of electrical energy in a circuit and verify Joule’s Law of Heating.

2. Requirements: Connecting wires, electric cells (battery), electrical resistor (R), voltmeter (V), ammeter (A), and plug key (switch).

3. Procedure

Set up the circuit as shown in the diagram, ensuring all components are properly connected.

Close the switch to allow current (I) to flow through the circuit.

Measure the current (I) using the ammeter.

Measure the potential difference (V_AB) across the resistor using the voltmeter.

Observe energy transfer:

The potential at point A is higher than at point B, as A is connected to the positive terminal of the cell.
As charge (Q) moves from A to B, electrical energy (V_AB × Q) is supplied by the battery to the resistor.
The resistor converts electrical energy into heat, increasing its temperature.

Electric circuit

Key Equations:

Electrical Power:

Heat Produced (Joule’s Law of Heating):

4. Conclusion: The experiment shows that a resistor converts electrical energy into heat, following Joule’s Law of Heating. The amount of heat produced depends on the current, resistance, and time for which the current flows. The unit of electrical power is 1 watt (W), defined as 1 joule per second.

Maharashtra State Board: Class 10

Joule’s Law of Heating and Electrical Power:

Joule’s law explains how electrical energy is converted into heat energy when an electric current flows through a resistor. The heat produced depends on the voltage, current, and resistance of the circuit.

Electrical Power and Heat Generation:

1. Definition of Electrical Power
Electrical power (P) is the rate at which electrical energy is supplied to a circuit. It is given by:

\[\mathrm{P=Electrical~power=\frac{Energy}{Timerequired}=\frac{V_{AB}Q}{t}=V_{AB}I}\]

where V_AB is the potential difference across the resistor, I is the current, and Q is the charge.

2. Heat Produced in a Resistor
The energy supplied by the cell in time t is:

By Ohm’s Law:

Substituting this in the heat equation:

\[\mathrm{H}=\mathrm{V}_{\mathrm{AB}}^{2}\times\frac{\mathrm{t}}{\mathrm{R}}\]

This equation is known as Joule’s Law of Heating, which states that the heat produced in a resistor is directly proportional to the square of the current, resistance, and time.

3. Unit of Electrical Power
Electrical power is also expressed as:

Since 1 Volt × 1 Ampere is equal to:

$\begin{array}{cc}1\text{Volt x 1 Amp}= & \frac{1\mathrm{J}}{1\mathrm{C}}\mathrm{x}\frac{1\mathrm{C}}{1\mathrm{s}}\end{array}$

$\begin{array}{rl}\frac{1\mathrm{J}}{1\mathrm{s}} & =\mathrm{W}\left(\mathrm{watt}\right)\end{array}$

Maharashtra State Board: Class 10

Key Points: Electric Circuit

Electric energy from a cell is used to do work on charges, which is converted into heat in a resistor or other forms, like motion in a motor.
The work done (energy) in moving a charge $Q$ across a potential difference is:
Heat produced (H) in a resistor over time $t$ is given by Joule’s Law of Heating:
According to Ohm’s Law:
Electrical power (P) is the rate of energy transfer and is calculated as:

Its unit is watt (W), where .

Related QuestionsVIEW ALL [115]

A child has drawn the electric circuit to study Ohm’s law as shown in Figure. His teacher told that the circuit diagram needs correction. Study the circuit diagram and redraw it after making all corrections.

Tabulate the different components of an electric circuit and their respective symbols.

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Name the device which is used to measure the strength of the electric current in an electric circuit.

Explain with the help of a labelled circuit diagram how you will find the resistance of a combination of three resistors, or resistance R₁, R₂ and R₃, joined in parallel. Also mention how you will connect the ammeter and the voltmeter in the circuit when measuring the current in the circuit and the potential difference across one of the three resistors of the combination.

When a circuit is open, _____ cannot pass through it.

How is a voltmeter connected in a circuit?

Match the column ‘A’ with column ‘B’.