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Questions and Answers
What direction do electric field lines point?
What direction do electric field lines point?
- From a neutral charge to a positive charge
- From negative to positive charges
- From positive to negative charges (correct)
- From a positive charge to a neutral charge
Which statement about electric field strength is true?
Which statement about electric field strength is true?
- It is a scalar quantity with no direction.
- It measures distance between two charges.
- It is defined as charge per unit force.
- It has the unit NC-1 or Vm-1. (correct)
According to Coulomb's law, the electrostatic force between two point charges is proportional to which of the following?
According to Coulomb's law, the electrostatic force between two point charges is proportional to which of the following?
- The square of the sum of their charges
- The difference of their charges
- The product of their charges (correct)
- The sum of their distances
What does the constant k in Coulomb's law represent?
What does the constant k in Coulomb's law represent?
What is the significance of the permittivity of free space, ε₀?
What is the significance of the permittivity of free space, ε₀?
What is the relationship between electric field strength and the direction a positive charge would accelerate?
What is the relationship between electric field strength and the direction a positive charge would accelerate?
Which of the following describes the nature of forces between point charges compared to gravitational force?
Which of the following describes the nature of forces between point charges compared to gravitational force?
What factor does the relative permittivity, εᵣ, affect?
What factor does the relative permittivity, εᵣ, affect?
What principle is used to determine the electric field strength of a point charge?
What principle is used to determine the electric field strength of a point charge?
What is the direction of the electric field lines around a positive point charge?
What is the direction of the electric field lines around a positive point charge?
Which of the following correctly represents the electric field strength formula in relation to point charge?
Which of the following correctly represents the electric field strength formula in relation to point charge?
What happens to a glass rod after it is rubbed with a silk cloth?
What happens to a glass rod after it is rubbed with a silk cloth?
How does the electric field strength change as the distance from a point charge increases?
How does the electric field strength change as the distance from a point charge increases?
How do electric fields behave around point charges?
How do electric fields behave around point charges?
Which statement differentiates gravitational and electric fields?
Which statement differentiates gravitational and electric fields?
What effect does a positively charged rod have on a neutral object nearby?
What effect does a positively charged rod have on a neutral object nearby?
What type of fields are described as having no dependence on position?
What type of fields are described as having no dependence on position?
The electric field produced by a point charge is characterized by what kind of shape?
The electric field produced by a point charge is characterized by what kind of shape?
Electric field lines originating from a negative point charge point:
Electric field lines originating from a negative point charge point:
What describes the distribution of electric field lines in relation to distance from a point charge?
What describes the distribution of electric field lines in relation to distance from a point charge?
What is the relationship between electric force and distance for point charges?
What is the relationship between electric force and distance for point charges?
Which of the following correctly describes the nature of charged particles like protons and electrons?
Which of the following correctly describes the nature of charged particles like protons and electrons?
How is electric field strength denoted mathematically?
How is electric field strength denoted mathematically?
Which of the following characteristics is NOT true for gravitational fields compared to electric fields?
Which of the following characteristics is NOT true for gravitational fields compared to electric fields?
What is the primary characteristic of electric fields produced by spherically charged spheres?
What is the primary characteristic of electric fields produced by spherically charged spheres?
Which of the following statements about electric fields is true?
Which of the following statements about electric fields is true?
What condition is required for the oil drops to hover midair between the charged plates?
What condition is required for the oil drops to hover midair between the charged plates?
How is the charge on the oil drops expressed mathematically?
How is the charge on the oil drops expressed mathematically?
What is the base value of the elementary charge determined by Millikan's experiment?
What is the base value of the elementary charge determined by Millikan's experiment?
What happens to the electrical energy when two opposite charges are brought closer together?
What happens to the electrical energy when two opposite charges are brought closer together?
What determines the potential energy of two point charges at a distance r apart?
What determines the potential energy of two point charges at a distance r apart?
What does the phrase 'work is done when a charge is brought in from infinity' imply?
What does the phrase 'work is done when a charge is brought in from infinity' imply?
What is the effect of increasing the voltage between parallel plates on the electric field?
What is the effect of increasing the voltage between parallel plates on the electric field?
What mathematical relationship expresses the electric field strength between charged parallel plates?
What mathematical relationship expresses the electric field strength between charged parallel plates?
What is the correct formula for calculating work done on a charge in an electric field?
What is the correct formula for calculating work done on a charge in an electric field?
If the electric potential at infinity is defined as 0, what does this imply for the potential difference between two points A and B?
If the electric potential at infinity is defined as 0, what does this imply for the potential difference between two points A and B?
In a uniform electric field created by parallel plates, what is the relationship between electric field strength E, potential difference V, and distance d?
In a uniform electric field created by parallel plates, what is the relationship between electric field strength E, potential difference V, and distance d?
How can the motion of a charged particle in a uniform electric field be compared to another type of motion?
How can the motion of a charged particle in a uniform electric field be compared to another type of motion?
What does it mean if the electric field is defined as $E = \frac{F}{Q}$?
What does it mean if the electric field is defined as $E = \frac{F}{Q}$?
When considering the work done per unit charge, how is the potential difference across two points in an electric field defined?
When considering the work done per unit charge, how is the potential difference across two points in an electric field defined?
What experimental setup is described using charged oil droplets in a vertical electric field?
What experimental setup is described using charged oil droplets in a vertical electric field?
In the context of work done and electric potential, what does the term 'work potential' refer to?
In the context of work done and electric potential, what does the term 'work potential' refer to?
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Study Notes
Electric Fields
- An electric field is a region where charged particles experience an electrostatic force.
- Electric fields are created by charged objects, and the strength of the field decreases with distance from the charge.
- Electric field lines point from a positive charge to a negative charge.
- Field lines are perpendicular to the surface of a charged object.
- Lines that connect charges represent attraction and those that remain separate represent repulsion.
Electric Field Strength
- The strength of an electric field is defined as the force per unit charge.
- Electric field strength is a vector quantity with both magnitude and direction.
- The unit of electric field strength is NC-1 or Vm-1.
Coulomb's Law
- Coulomb's law states that the force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them.
- The constant of proportionality is k = 8.99 x 10^9 Nm^2 C^-2.
Electric Field of a Point Charge
- The electric field strength of a point charge Q at a distance r is given by E = Q / (4𝜋𝜀₀r^2).
- This equation shows that the electric field decreases with the square of the distance from the charge.
Gravitational and Electric Fields Compared
- The similarities between gravitational and electric fields can be used to model the motion of charged particles in an electric field.
- Both fields are proportional to the product of two interacting properties (mass for gravity, charge for electricity) divided by the square of the distance between them.
Uniform Electric Fields
- A uniform electric field is a field where the strength is constant in space.
- Uniform electric fields are produced between two oppositely charged parallel plates.
- A charged particle placed in a uniform field will experience a constant force.
- Electric field strength can be defined as E = V/d where V is the potential difference across the plates and d is the distance between them.
Work Done and Electric Potential
- Work done is a measure of energy transferred by a force acting over a distance.
- Work done moving a charge in an electric field is defined by the product of the force and the distance.
- Electric potential difference is defined as the work done per unit charge moving between two points.
- The electric potential at a point is the work done per unit charge to bring a positive charge from infinity to that point.
- The electric potential at infinity is usually defined as 0.
- Potential difference can be calculated as V = E*d for a uniform electric field.
Motion of a Charged Particle in a Uniform Electric Field
- The motion of a charged particle in a uniform electric field can be compared to that of a massive particle in a gravitational field.
- Millikan's oil drop experiment determined the elementary charge by balancing the weight of charged oil droplets with the force caused by a uniform electric field.
Work Done on Point Charges
- Work is done when a charge is brought from infinity to a distance r from a point charge.
- This work is the electrical energy of the system.
- The electrical energy of a system with two charges can be positive or negative depending on the sign of the charges.
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