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Questions and Answers
A parallel-plate capacitor has a capacitance of $C$. If the distance between the plates is doubled and the area of the plates is halved, what is the new capacitance?
A parallel-plate capacitor has a capacitance of $C$. If the distance between the plates is doubled and the area of the plates is halved, what is the new capacitance?
- $C/4$ (correct)
- $C/2$
- $2C$
- $C$
A resistor with resistance $R$ is connected to a battery with voltage $V$. If the resistance is doubled and the voltage is halved, what happens to the power dissipated by the resistor?
A resistor with resistance $R$ is connected to a battery with voltage $V$. If the resistance is doubled and the voltage is halved, what happens to the power dissipated by the resistor?
- It increases by a factor of 2.
- It decreases by a factor of 4.
- It decreases by a factor of 8. (correct)
- It stays the same.
Two point charges, $+q$ and $-q$, are separated by a distance $d$. What is the magnitude of the electric field midway between the charges?
Two point charges, $+q$ and $-q$, are separated by a distance $d$. What is the magnitude of the electric field midway between the charges?
- $\frac{8 k q}{d^2}$ (correct)
- $\frac{2 k q}{d^2}$
- $\frac{k q}{d^2}$
- 0
A wire of length $L$ and cross-sectional area $A$ has resistance $R$. If the wire is stretched to twice its original length, what is the new resistance, assuming the volume remains constant?
A wire of length $L$ and cross-sectional area $A$ has resistance $R$. If the wire is stretched to twice its original length, what is the new resistance, assuming the volume remains constant?
A proton is moving with a velocity $v$ perpendicular to a uniform magnetic field $B$. What is the effect of the magnetic field on the proton's speed and kinetic energy?
A proton is moving with a velocity $v$ perpendicular to a uniform magnetic field $B$. What is the effect of the magnetic field on the proton's speed and kinetic energy?
A metal wire's resistance is found to increase. Which of the following changes would most likely cause this?
A metal wire's resistance is found to increase. Which of the following changes would most likely cause this?
In a parallel circuit, if one of the branches is removed, how will the total current supplied by the voltage source change?
In a parallel circuit, if one of the branches is removed, how will the total current supplied by the voltage source change?
A negatively charged rod is brought near a neutral metallic sphere, but does not touch it. The sphere is then briefly touched by a grounding wire. What is the final charge on the sphere?
A negatively charged rod is brought near a neutral metallic sphere, but does not touch it. The sphere is then briefly touched by a grounding wire. What is the final charge on the sphere?
A circuit contains a 12V battery and two resistors in series, with resistances of 4Ω and 8Ω. What is the current flowing through the 4Ω resistor?
A circuit contains a 12V battery and two resistors in series, with resistances of 4Ω and 8Ω. What is the current flowing through the 4Ω resistor?
Which of the following actions will result in charging an object by conduction?
Which of the following actions will result in charging an object by conduction?
Why is alternating current (AC) preferred over direct current (DC) for long-distance power transmission?
Why is alternating current (AC) preferred over direct current (DC) for long-distance power transmission?
A parallel plate capacitor is charged and then disconnected from the battery. If the distance between the plates is increased, what happens to the voltage across the capacitor?
A parallel plate capacitor is charged and then disconnected from the battery. If the distance between the plates is increased, what happens to the voltage across the capacitor?
Given a circuit with a voltage source of 9V and a resistor of 3Ω, calculate the power dissipated by the resistor.
Given a circuit with a voltage source of 9V and a resistor of 3Ω, calculate the power dissipated by the resistor.
When a balloon is rubbed against hair, electrons are transferred from the hair to the balloon. What are the resulting charges on the balloon and the hair?
When a balloon is rubbed against hair, electrons are transferred from the hair to the balloon. What are the resulting charges on the balloon and the hair?
In a simple electrical circuit, what happens to the current if the voltage is doubled and the resistance is halved?
In a simple electrical circuit, what happens to the current if the voltage is doubled and the resistance is halved?
Flashcards
Conductors
Conductors
Materials that allow electric charge to flow freely
Insulators
Insulators
Materials that resist the flow of electric charge
Electrostatics
Electrostatics
The accumulation of electric charge on a surface
Electric Current
Electric Current
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Electricity
Electricity
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Electric Charge
Electric Charge
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Charging by Friction
Charging by Friction
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Charging by Conduction
Charging by Conduction
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Charging by Polarization
Charging by Polarization
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Current
Current
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Resistance
Resistance
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Series Circuit
Series Circuit
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Parallel Circuit
Parallel Circuit
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Study Notes
- Study guide covering electrostatics and electricity.
Conductors vs. Insulators
- Conductors allow charges to flow easily; examples are metals like copper and aluminum.
- Conductors have loosely bound outer electrons.
- Insulators resist electrical flow; examples include rubber, plastic, wood, dry air, and glass.
- Insulators have electrons tightly bound to atoms.
Electric Charges
- Two types of electric charges are positive (+) and negative (-).
- Like charges repel each other, while unlike charges attract.
- Electrons have identical negative charges.
- Protons have identical positive charges.
- Charge is conserved, meaning it cannot be created or destroyed.
Methods of Charging
- Charging by friction occurs when materials are rubbed together.
- During charging by friction, electrons transfer from one material to another, resulting in one material becoming positively charged and the other negatively charged.
- Rubbing a balloon on hair or walking on a carpet are examples of charging by friction.
- Charging by conduction involves direct contact between materials, allowing charges to transfer through physical contact.
- Both objects end up with the same type of charge after charging by conduction.
- Charging by polarization does not require direct contact, but the charges are redistributed due to a nearby charged object.
- A charged object attracting neutral pieces of paper is an example of charging by polarization.
Current Electricity
- Current is the rate of flow of electric charge, measured in amperes (A).
- 1 ampere equals 1 coulomb per second.
- Conventional current flows from positive to negative.
- Electron flow is opposite to conventional current.
Resistance
- Resistance opposes the flow of current and is measured in ohms (Ω).
- Factors affecting resistance:
- Length (longer = more resistance)
- Cross-sectional area (wider = less resistance)
- Temperature (higher = more resistance in most materials)
- Material type
Circuit Basics
- Series Circuits
- Components are connected end-to-end.
- The same current flows through all components in a series circuit.
- Voltage is divided among components.
- Total resistance equals the sum of individual resistances.
- Parallel Circuits
- Components are connected across each other.
- The same voltage exists across all components in a parallel circuit.
- Current is divided among paths.
- Total resistance is less than the smallest individual resistance.
- Short Circuits
- Short circuits provide a path of very low resistance.
- They can damage components and batteries.
- Usually unintentional and dangerous, often caused by direct wire connection.
Types of Current
- Direct Current (DC)
- Current flows in one direction.
- Voltage is constant.
- Batteries and solar cells are examples of DC sources.
- Used in most electronic devices.
- Alternating Current (AC)
- Current periodically reverses direction.
- Voltage varies.
- Standard in household outlets.
- More efficient for power transmission.
Ohm's Law and Related Concepts
- Ohm's Law
- V = IR (Voltage = Current × Resistance)
- Ohm's Law is used to analyze circuit behavior.
- It shows a linear relationship for many materials.
- Represented as a straight line through the origin for ohmic materials.
- Power in Circuits
- P = VI (Power = Voltage × Current)
- Measured in watts (W).
- Indicates the rate of energy transfer.
Study Tips
- Draw diagrams to visualize charge movement.
- Practice calculating current, voltage, and resistance.
- Build simple circuits to understand connections.
- Memorize the different charging methods.
- Understand real-world applications of each concept.
Common Misconceptions
- Electricity doesn't take the "shortest" path, it takes ALL paths
- Current is not "used up" as it flows through a circuit
- Voltage is not the same as current
- Higher voltage doesn't always mean higher current
- Charge cannot be created or destroyed, only transferred
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Description
Study guide covering electrostatics and electricity. It discusses conductors, insulators, electric charges, and methods of charging objects. Examples include charging by friction, like rubbing a balloon on hair.
