Questions and Answers
A coulomb of charge that passes through a 6-volt battery is given
Which statement is correct?
Electrons move in an electrical circuit
Heat a copper wire and its electric resistance
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Stretch a copper wire so that it is thinner and the resistance between it
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The primary source of electrons in an ordinary electric circuit is
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The source of electrons lighting an incandescent AC lightbulb is
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A woman experiences an electric shock. The electrons making the shock come from the
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In a common DC circuit, electrons move at speeds of
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When a light switch is turned on in a DC circuit, the average speed of electrons in the lamp is
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Modern automobile headlights are connected in
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There are electrons in the filament of the AC lamp in your bedroom. When you turn on the lamp and it glows, the glowing comes from
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A 100-watt lamp glows brighter than a 25-watt lamp. The electrical resistance of the 100-watt lamp must be
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In an electric circuit, the safety fuse is connected to the circuit in
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When a pair of 1-ohm resistors are connected in series, their combined resistance is
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A capacitor is used to store
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The number of electrons delivered daily to an average American home by an average power utility in the mid 1980s was
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Two lamps, one with a thick filament and one with a thin filament, are connected in series. The current is greater in the lamp with the
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Two lamps, one with a thick filament and one with a thin filament, are connected in parallel to a battery. The voltage is greatest across the lamp with the
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Two lamps, one with a thick filament and one with a thin filament of the same material, are connected in parallel to a battery. The current is larger in the lamp with the
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Compared to the resistance of two resistors connected in series, the same two resistors connected in parallel have
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If you plug an electric toaster rated at 110 V into a 220-V outlet, the current in the toaster will be about
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When a 60-watt light bulb is connected to a 120-volt source the current in the light bulb is
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If 0.8 A of current flows through a light bulb connected to a 120 V outlet, the power consumed is
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The headlights, radio, and defroster fan in an automobile are connected in
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Compared to the filament thickness of a 60 W light bulb, the filament of a 100 W light bulb will be
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Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry
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Compared to a single lamp connected to a battery, two lamps connected in parallel to the same battery will carry
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An electric heater is rated at 300 W when used in a 110-V circuit. The safety fuse in the circuit can handle 15 A of current. How many heaters can be safely operated in the circuit?
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A heater uses 20 A when used in a 110-V line. If electric power costs 10 cents per kilowatt hour, the cost of running the heater for 10 hours is
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Connect a pair of lamps in series and you draw current from the connected battery. Connect the same lamps in parallel and you draw
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Three resistors, 1-ohm, 2-ohm, and 3-ohm are connected in parallel. If they were connected in series instead their equivalent resistance would be
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The ratio of the potential difference across a metallic conductor to the current in the conductor is known as
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What condition must exist between two points in a conductor in order to maintain a flow of charge?
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Study Notes
Electric Current Concepts
- A coulomb of charge passing through a 6-volt battery provides 6 joules of energy.
- Charge must flow in a closed circuit; voltage can exist in both open and closed circuits.
- Electrons in an electric circuit primarily move due to interaction with an established electric field.
- Heating a copper wire increases its electric resistance.
- Stretching a copper wire results in increased resistance due to its reduced thickness.
Sources and Flow of Electrons
- The primary source of electrons in an electric circuit is the circuit itself (e.g., batteries).
- Electrons illuminating an incandescent light bulb originate from atoms in the filament.
- Electric shocks experienced by individuals are due to electrons from their bodies.
Movement and Speed of Electrons
- In common DC circuits, electrons move at speeds of a fraction of a centimeter per second.
- When a light switch is engaged, the average speed of electrons in a lamp is less than 1 cm/s.
Circuit Configurations
- Modern automobile headlights are wired in parallel for consistent brightness.
- When a lamp glows, it is due to the same electrons that flow through the circuit, not different ones.
- A higher wattage lamp (100-watt) has lower resistance compared to a lower wattage lamp (25-watt).
Current and Resistance in Resistors
- Safety fuses are incorporated in series with the electrical circuit to protect against overload.
- Two 1-ohm resistors in series yield a total resistance of 2 ohms; in parallel they give 0.5 ohms.
- Capacitors are capable of storing both charge and energy.
Power Consumption and Safety
- In the mid-1980s, average daily electron delivery to an American home was in the billions.
- Comparing filament thickness, a 100-watt bulb has a thicker filament than a 60-watt bulb.
- The voltage across parallel-connected lamps remains constant, regardless of filament thickness.
Electrical Ratings and Calculations
- If a toaster rated at 110 V is plugged into a 220 V outlet, the current will be about twice what it is intended to be.
- A 60-watt bulb connected to a 120-volt source draws 0.5 A of current.
- A light bulb drawing 0.8 A from a 120 V outlet consumes 96 watts of power.
Current Flow in Parallel and Series
- Automotive accessories like headlights and radios are connected in parallel with individual switches for control.
- In a series configuration, current is the same across all components while it varies in parallel circuits.
- Connecting identical lamps in series reduces the overall current compared to a single lamp.
Resistance in Series vs. Parallel
- Two identical lamps in parallel draw more current than one lamp in series due to available voltage across both.
- In a series connection, the equivalent resistance of three resistors (1-ohm, 2-ohm, and 3-ohm) would total 6 ohms, making it 9 times greater than their parallel configuration.
Concepts of Voltage and Current
- The ratio of potential difference (voltage) to current is known as resistance.
- For charge flow in a conductor, no special conditions like a magnetic field or a high resistance need to be present—just a potential difference.
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Description
Test your knowledge of electric current concepts from Chapter 23 of Conceptual Physics. This quiz includes multiple-choice questions that focus on definitions and principles related to circuits and charges. Challenge yourself and enhance your understanding of how current behaves in different scenarios.