Electric Circuit Fundamentals

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Questions and Answers

What is the formula for applying Ohm's law to the entire circuit?

R=VI

I=R/V

I=VR

V=IR (correct)

What is the formula for the total resistance of the combination of resistors joined in series?

Rs = R1 + R2 + R3 (correct)

Rs = R1 / R2 / R3

Rs = R1 × R2 × R3

Rs = R1 - R2 - R3

What is the total resistance of the circuit in the example problem?

6 Ω

20 Ω

24 Ω (correct)

4 Ω

What is the voltage across the electric lamp and conductor in the example problem?

6 V Signup and view all the answers

What is the current through the circuit in the example problem?

0.25 A Signup and view all the answers

What is the formula used to calculate the current through the circuit?

I = V/Rs Signup and view all the answers

What is the resistance of the electric lamp in the example problem?

20 Ω Signup and view all the answers

What is the total potential difference across the two terminals of the battery in the example problem?

6 V Signup and view all the answers

What gases are usually used to fill bulbs to prolong the life of the filament?

Nitrogen and argon Signup and view all the answers

What is the primary function of a fuse in electric circuits?

To protect circuits and appliances from excessive current Signup and view all the answers

What is the characteristic of the metal or alloy used to make a fuse wire?

Low melting point Signup and view all the answers

What is the unit of electric power?

Watt Signup and view all the answers

What is the rate at which electric energy is consumed in an electric circuit?

Electric power Signup and view all the answers

Why is a 5 A fuse used for an electric iron that consumes 1 kW electric power?

Because it matches the calculated required current Signup and view all the answers

What is the term used to describe the rate of doing work?

Power Signup and view all the answers

What is the effect of excessive current flowing through a fuse wire?

It melts the fuse wire and breaks the circuit Signup and view all the answers

What is the direction of electric current in a circuit?

From the positive terminal to the negative terminal Signup and view all the answers

What is the unit of electric current?

Ampere Signup and view all the answers

What is the formula to calculate the amount of electric charge?

Q = It Signup and view all the answers

What is the amount of electric charge that flows through the circuit in the example?

300 C Signup and view all the answers

What is the average speed of electrons in a conductor?

Average drift speed Signup and view all the answers

How do electrons move in a perfect solid crystal?

Smoothly and easily Signup and view all the answers

What is the role of the plug key in the circuit?

To disconnect the circuit Signup and view all the answers

What is the purpose of an ammeter in the circuit?

To measure the current Signup and view all the answers

What is the order of the drift speed of electrons in a typical copper wire carrying a small current?

1 mm s-1 Signup and view all the answers

Why does an electric bulb light up immediately when we turn the switch on?

Because the electric potential difference sets the charges in motion in the conductor Signup and view all the answers

What is necessary for the flow of charges in a conducting metallic wire?

Electric potential difference Signup and view all the answers

What generates the potential difference across the terminals of an electric cell?

Chemical action Signup and view all the answers

What is the role of gravity in the flow of charges in a conducting metallic wire?

It has no role to play Signup and view all the answers

What is the purpose of a battery in a conducting circuit?

To generate electric potential difference Signup and view all the answers

What is the analogy used to describe the flow of charges in a conducting metallic wire?

Flow of water Signup and view all the answers

What happens when a cell is connected to a conducting circuit element?

The electric potential difference sets the charges in motion Signup and view all the answers

What is the potential difference across the resistor when the current is 2.0 A?

6.7 V Signup and view all the answers

A 12 V battery is connected across an unknown resistor, and a current of 2.5 mA flows. What is the resistance of the resistor?

4.8 Ω Signup and view all the answers

A battery of 9 V is connected in series with resistors of 0.2 Ω, 0.3 Ω, 0.4 Ω, 0.5 Ω, and 12 Ω, respectively. What is the current that would flow through the 12 Ω resistor?

0.5 A Signup and view all the answers

How many 176 Ω resistors are required to carry 5 A on a 220 V line?

4 Signup and view all the answers

How can three resistors, each of resistance 6 Ω, be connected to have a resistance of 9 Ω?

Two in parallel and one in series Signup and view all the answers

Several electric bulbs are rated 10 W and are designed to be used on a 220 V electric supply line. What is the maximum number of lamps that can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A?

20 Signup and view all the answers

A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What is the current in the parallel case?

10 A Signup and view all the answers

Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What is the total current drawn from the line if the supply voltage is 220 V?

1.5 A Signup and view all the answers

Study Notes

Electric Circuits and Current

Electric current flows in a circuit from the positive terminal of the cell to the negative terminal through the circuit components (e.g., bulb and ammeter).
A schematic diagram of an electric circuit consists of a cell, electric bulb, ammeter, and plug key.

Electric Charge and Flow

The flow of electric charge is similar to the flow of water, requiring a pressure difference (electric potential difference) to occur.
In a conducting metallic wire, electrons move only if there is a potential difference along the conductor.
The potential difference is produced by a battery, which generates a potential difference across its terminals even when no current is drawn.

Electric Current and Drift Speed

The motion of electrons in a conductor is different from that of charges in empty space.
When a steady current flows through a conductor, the electrons move with a certain average drift speed, which is very small (e.g., 1 mm s-1 in a typical copper wire).

Electric Potential and Potential Difference

Electric potential difference (or voltage) is the driving force behind electric current flow.
Applying Ohm's law to the entire circuit, we have V = IR, where V is the potential difference, I is the current, and R is the resistance.

Resistors in Series

When several resistors are connected in series, the total resistance of the combination (Rs) equals the sum of their individual resistances (R1, R2, R3, etc.).
The total resistance of the combination is greater than any individual resistance.

Electric Power and Energy

Electric power is the rate of consumption of energy, which is also the rate at which electric energy is dissipated or consumed in an electric circuit.
The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor can be used to plot a graph and calculate the resistance of the resistor.

Applications of Electric Circuits

Electric lamps are usually filled with chemically inactive nitrogen and argon gases to prolong the life of the filament.
Joule's heating is used in fuses, which protect circuits and appliances by stopping the flow of any unduly high electric current.
Electric power is used in various applications, such as electric irons, which consume a certain amount of power when operated at a specific voltage.

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Description

This quiz covers the basics of electric circuits, including the flow of electric current and the components of a circuit. Test your understanding of electric circuits and their components.