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Questions and Answers
Which of the following statements is true regarding the force between electric charges?
Which of the following statements is true regarding the force between electric charges?
- Like charges attract each other.
- Opposite charges repel each other.
- The force is directly proportional to the distance between the charges.
- The force is inversely proportional to the square of the distance between the charges. (correct)
The electric charge of an isolated system can be changed.
The electric charge of an isolated system can be changed.
False (B)
What experimental evidence supports the quantization of electric charge?
What experimental evidence supports the quantization of electric charge?
Millikan's oil drop experiment
Materials with plenty of free electrons are classified as ______.
Materials with plenty of free electrons are classified as ______.
What is the role of grounding (earthing) in transferring electric charge?
What is the role of grounding (earthing) in transferring electric charge?
The electric field strength is a scalar quantity.
The electric field strength is a scalar quantity.
According to Coulomb's Law, what parameters affect the magnitude of the electrostatic force between two charged particles?
According to Coulomb's Law, what parameters affect the magnitude of the electrostatic force between two charged particles?
Electric field lines point away from ______ charges and towards ______ charges.
Electric field lines point away from ______ charges and towards ______ charges.
What happens to the charge on two identical conducting spheres when they touch?
What happens to the charge on two identical conducting spheres when they touch?
Electric field lines can cross each other.
Electric field lines can cross each other.
What is electrostatic induction?
What is electrostatic induction?
The electric field inside a conductor in electrostatic equilibrium is ______.
The electric field inside a conductor in electrostatic equilibrium is ______.
Which of the following processes involves the direct transfer of electrons?
Which of the following processes involves the direct transfer of electrons?
The direction of the electric field is defined as the direction of the force on a negative test charge.
The direction of the electric field is defined as the direction of the force on a negative test charge.
What is the purpose of a gold-leaf electroscope?
What is the purpose of a gold-leaf electroscope?
The force experienced by a charge in an electric field is given by $F = ______$
The force experienced by a charge in an electric field is given by $F = ______$
Which of the following is the correct formula for Coulomb's Law?
Which of the following is the correct formula for Coulomb's Law?
The value of k in Coulomb's Law is approximately $9.0 \times 10^9 Nm^2C^{-2}$.
The value of k in Coulomb's Law is approximately $9.0 \times 10^9 Nm^2C^{-2}$.
In which direction will an electron move if released in a uniform electric field?
In which direction will an electron move if released in a uniform electric field?
The electric field strength (E) is defined as the ______ per unit charge.
The electric field strength (E) is defined as the ______ per unit charge.
What does the Millikan oil drop experiment demonstrate?
What does the Millikan oil drop experiment demonstrate?
Insulators contain plenty of free electrons which can move when an electric field is present.
Insulators contain plenty of free electrons which can move when an electric field is present.
What is the relationship between electric field line density and electric field strength?
What is the relationship between electric field line density and electric field strength?
If two identical conducting spheres with charges of 4 μC and -12 μC touch, the final charge on each sphere after separation will be ______ μC.
If two identical conducting spheres with charges of 4 μC and -12 μC touch, the final charge on each sphere after separation will be ______ μC.
Match the term with the description
Match the term with the description
What is the potential energy released if a charged particle is moved by the electric field from one potential $V_a$ to another $V_b$?
What is the potential energy released if a charged particle is moved by the electric field from one potential $V_a$ to another $V_b$?
The electric field from a single point charge Q at a point a distance r away is represented by $E_p = k\frac{Q}{r^2}$
The electric field from a single point charge Q at a point a distance r away is represented by $E_p = k\frac{Q}{r^2}$
What must be performed in order to move a charge of 5.0 µC from the negative to the positive plate if a potential difference of 250 V is established between the plates?
What must be performed in order to move a charge of 5.0 µC from the negative to the positive plate if a potential difference of 250 V is established between the plates?
An electron accelerated through a potential difference of 1 V gains an energy of 1 ______, which is equivalent to $1.6 \times 10^{-19}$ Joules.
An electron accelerated through a potential difference of 1 V gains an energy of 1 ______, which is equivalent to $1.6 \times 10^{-19}$ Joules.
What is the direction of the electric field inside a charged parallel-plate capacitor, assuming the plates are large and closely spaced?
What is the direction of the electric field inside a charged parallel-plate capacitor, assuming the plates are large and closely spaced?
Flashcards
Direction of Electric Forces
Direction of Electric Forces
The direction of attraction or repulsion between electric charges. Opposite charges attract, like charges repel.
Coulomb's Law
Coulomb's Law
Describes the force between two point charges as proportional to the product of the charges and inversely proportional to the square of the distance between them.
Conservation of Electric Charge
Conservation of Electric Charge
The total electric charge in an isolated system remains constant. Charge is neither created nor destroyed.
Electric Field Strength
Electric Field Strength
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Electric Field Lines
Electric Field Lines
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Field Line Density
Field Line Density
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Uniform Electric Field
Uniform Electric Field
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Non-Crossing Field Lines
Non-Crossing Field Lines
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Conductors and Free Electrons
Conductors and Free Electrons
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Conservation of Charge
Conservation of Charge
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Charging by Induction
Charging by Induction
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Work and Potential Difference
Work and Potential Difference
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Potential Energy Release
Potential Energy Release
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Electronvolt
Electronvolt
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Study Notes
- Electric and magnetic fields exist
- Standard and higher level students should study this for 8 hours
Electric Charge Types and Forces
- There are two types of electric charge
- The direction of forces between the two types should be understood
- Like charges repel, opposite charges attract
Coulomb's Law
- Coulomb's Law is F = k(q1q2/r^2) for charged bodies treated as point charges
- k = 1/(4πε₀)
- It describes the force between two charged objects
- k is Coulomb's Law Constant at 9.0 × 10^9 Nm²C⁻²
- ε₀ is the permittivity of free space, equaling 8.85 x 10⁻¹² Fm⁻¹
Electric Charge
- Electric charge is measured in Coulombs (C)
- One electron has a charge of -1.6 x 10⁻¹⁹ C
- Electric charge is conserved; the total charge of an isolated system remains constant
- Atoms have the same number of protons and electrons and are NEUTRAL overall
- Electrons are on the outside of atoms so are able to move around (causing electrical effects)
- Electric charge can be transferred between bodies using friction, electrostatic induction, and contact, including grounding
Conductors and Insulators
- Conductors contain plenty of free electrons that can move when an electric field is present
- Insulators contain very few free electrons
- Objects can gain charge by friction, which involves the removal or deposition of electrons
Charging by Electrostatic Induction
- Objects can be charged by electrostatic induction
- A charged rod brought near an insulated conductor forces electrons to move within the conductor
- If the conductor is earthed, electrons will flow into the earth, leaving the conductor positively charged
Gold-Leaf Electroscope
- The gold-leaf electroscope can be used to detect charge
- It includes a metal cap, metal rod, insulating plug, metal plate, gold leaf, glass window, and a wooden or metal case that is earthed
- A negatively charged rod placed near the ball of the electroscope forces electrons down to the foil, causing it to diverge.
- If the electroscope is earthed and the rod then removed, the electroscope remains positively charged; a positively charged rod would result in a negatively charged electroscope.
Electric Field Strength
- Electric field strength is given by E = F/q
- Electric field lines show the direction of the field and force on a positive charge
- The closer the lines, the stronger the field
- Electric field lines cannot cross because the field can't be in two directions at once
- The more lines shown starting from a charge, the greater the charge
- The electric field from a single point charge Q at a distance r is E = kQ/r²
- In electrostatics, the electric field is zero inside any conducting body because charges are not in motion
Uniform Electric Fields
- An uniform electric field has constant magnitude and direction
- A uniform electric field is generated between two oppositely charged parallel plates
- Field lines curve near the edges, indicating the field is no longer uniform there (edge effect)
- Uniform electric field strength between parallel plates: E = V/d
Millikan's Experiment
- Millikan's experiment (1910-1911) measured the charge of an electron
- Oil drops charged by X-rays were allowed to enter a uniform electric field between parallel plates
- The weight of the oil drop is balanced by the electric force: mg = qE
- To measure charge, Millikan needed to find the mass of the oil drop
- He measured the terminal speed of the oil drop to determine its radius, mass, and charge
- He found that each charge was an integral multiple of a basic unit, e = 1.6 x 10⁻¹⁹ C
Electric Potential
- Work done to move a charge q from point A to point B: W = q(VB - VA)
- Voltage is energy used per unit charge (joules per coulomb)
Electronvolt
- Electronvolt is the work done when a charge equal to one electron charge is taken across a potential difference of one volt
- 1 eV = 1.6 × 10⁻¹⁹ C x 1 V = 1.6 x 10⁻¹⁹ J
- In calculations, electronvolts must be converted to joules, the SI unit of energy
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