Electric Current and Potential Difference

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Questions and Answers

A copper wire is carrying a current of 2 A. How many coulombs of electric charge pass through a cross-section of the wire in 5 seconds?

  • 0.4 coulombs
  • 10 coulombs (correct)
  • 2.5 coulombs
  • 7 coulombs

If a conductor's length is doubled and its cross-sectional area is halved, how does its resistance change, assuming the material and temperature remain constant?

  • The resistance is quadrupled. (correct)
  • The resistance remains the same.
  • The resistance is halved.
  • The resistance doubles.

A 12V battery is connected to a resistor. If the current flowing through the resistor is 3A, what is the resistance of the resistor?

  • 15 Ω
  • 9 Ω
  • 36 Ω
  • 4 Ω (correct)

Which of the following changes will decrease the resistance of a metal wire?

<p>Using a material with lower resistivity (B)</p> Signup and view all the answers

What is the potential difference between two points if 60 J of work is required to move a charge of 5 C between those points?

<p>12 V (C)</p> Signup and view all the answers

Substance A has a resistivity of $1.7 * 10^{-8} Ω⋅m$, and substance B has a resistivity of $5.6 * 10^{-8} Ω⋅m$. If wires of the same length and cross-sectional area are made from each substance, which wire will allow more current to flow for a given voltage?

<p>Wire A, because it has lower resistivity. (C)</p> Signup and view all the answers

A wire has a resistance of 10 Ω. If both its length and diameter are doubled, what will be the new resistance of the wire?

<p>5 Ω (D)</p> Signup and view all the answers

What is the relationship between conductivity ($σ$) and resistivity ($ρ$)?

<p>$σ = 1/ρ$ (C)</p> Signup and view all the answers

A circuit contains three resistors in series with values of 10 ohms, 20 ohms, and 30 ohms. If a 12V battery is connected across this series combination, what is the current flowing through the 20-ohm resistor?

<p>0.2 A (A)</p> Signup and view all the answers

Two resistors, 4 ohms and 6 ohms, are connected in parallel. If the voltage source is 12V, what is the total current supplied by the source?

<p>5 A (C)</p> Signup and view all the answers

A 100-watt light bulb is connected to a 120V AC power source. What is the RMS current flowing through the light bulb?

<p>0.83 A (B)</p> Signup and view all the answers

A 240V AC power supply is used to power a heating element with a resistance of 20 ohms. How much electrical energy is consumed by the heating element in 2 hours?

<p>$4.15 \times 10^6$ J (D)</p> Signup and view all the answers

A sinusoidal AC voltage has a peak value of 340 V. What is its RMS value?

<p>240 V (B)</p> Signup and view all the answers

Which of the following is NOT a safety measure used to prevent electrical hazards?

<p>Using uninsulated tools when working with live wires. (A)</p> Signup and view all the answers

A circuit breaker is designed to trip at 20 A. If the circuit is connected to a 120 V supply, what is the maximum power that can be safely drawn from the circuit?

<p>2400 W (C)</p> Signup and view all the answers

A battery with an EMF of 12V has an internal resistance of 0.5 ohms. If this battery is connected to a 3.5-ohm resistor, what is the current flowing through the resistor?

<p>3 A (A)</p> Signup and view all the answers

If the current flowing through a 5-ohm resistor is described by the equation $I(t) = 2\sin(314t)$ A, what is the RMS current?

<p>$\sqrt{2}$ A (A)</p> Signup and view all the answers

A parallel circuit has three branches with resistances of 10 ohms, 20 ohms, and 30 ohms. If the applied voltage is 6V, what is the current through the 10-ohm resistor?

<p>0.6 A (D)</p> Signup and view all the answers

Flashcards

Current Electricity

The flow of electric charge through a conductor.

Electric Current (I)

The rate of flow of electric charge.

Potential Difference (V)

The difference in electric potential between two points.

Resistance (R)

Opposition to the flow of electric current.

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Ohm's Law

Voltage equals current times resistance: V = IR.

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Resistivity (ρ)

A material's inherent ability to resist current flow.

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Resistance Factors

The length and area affect resistance.

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Conductivity (σ)

Measure of how easily current flows through a material.

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Series Circuit

Components connected end-to-end along a single path.

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Parallel Circuit

Components connected across each other, providing multiple paths for current.

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Electrical Power (P)

Rate at which electrical energy is converted to other forms.

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Electrical Energy (E)

Energy transferred by an electric current.

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Direct Current (DC)

Flow of electric charge in only one direction.

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Alternating Current (AC)

Flow of electric charge that periodically reverses direction.

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RMS Values

Effective values of AC voltage and current.

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Insulation

Prevents contact with live conductors.

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Circuit Breakers/Fuses

Interrupts current flow when it exceeds a safe level.

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Study Notes

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