40 Questions
What is the symbol used to denote an electric charge?
Q
What is the result of like charges interacting with each other?
They repel each other
What happens to the number of electrons in a body that is positively charged?
It decreases
What is the purpose of rubbing a rod to charge it?
To transfer energy
What is the result of unlike charges interacting with each other?
They attract each other
What is a characteristic of an uncharged body?
It contains an equal number of protons and electrons
What is the primary method of conduction in metals?
Movement of free electrons
What is the type of charge that a body has if it contains an excess of electrons?
Negative charge
What is the purpose of the fundamental law of action between charges?
To describe the interaction between like and unlike charges
What type of materials do not allow electric charges to move easily through them?
Insulators
What is the result of rubbing a glass rod with silk?
The glass rod becomes positively charged
What occurs when a charged body is brought close to an uncharged body?
The redistribution of charges on the uncharged body occurs
What type of materials share both the properties of conductors and insulators?
Semiconductors
What is the result of charging a body by friction?
The body can be either positively or negatively charged
What happens to the charges on a conductor after a charged rod is removed?
The positive and negative charges on the conductor return to their undisturbed positions
What is the term for charging a body by rubbing two substances together?
Charging by friction
What is the phenomenon of separation of charges in a conductor due to a nearby charged body known as?
Electrostatic induction
What happens to a conductor when it is earthed momentarily while under the influence of a charged body?
It becomes permanently charged
What is the result of charging a conductor by contact with another charged conductor?
The total charge remains the same
What is the direction of an electric field at a point?
The direction of the force on a small positive charge
Electric lines of force emanate from?
Positive charges
What is the relationship between the force between two electrically charged bodies and the distance between them?
The force is inversely proportional to the square of the distance
What is the electric force between two point charges directly proportional to?
The product of the charges
What is the electric field strength also known as?
Electric intensity
What is the unit of charge in the S.I system?
Coulomb
What is the formula for electric field strength E?
E = F/Q
What is the direction of the electric field strength E?
The direction of the force on a positive charge
What is the unit of electric field strength E?
Newton per Coulomb
What is the relative permittivity of a medium?
The ratio of its material permittivity to that of a vacuum
What is the formula for the relative permittivity of a medium?
εr = ε/ε0
What is the constant k in the formula F = kq1q2/r^2?
4πε0
What is the electric field defined as?
A region where an electric force is felt
What is the practical unit of electric field strength?
Volt per metre (V m−1)
What is the formula for the electric field strength due to a point charge?
E = kq / r²
What is the value of k in the formula for electric field strength?
4πϵ₀
What is the direction of the net force acting on the +15C charge?
At an angle of 27.60° to the −20C charge
What is the magnitude of the force of attraction between +15C and −20C?
3 × 10¹¹ N
What is the magnitude of the net force acting on the +15C charge?
6.5 × 10¹¹ N
What is the angle of the net force acting on the +15C charge?
27.60°
What is the formula for the electric field strength at a point P due to two point charges?
E = k(q₁ + q₂) / r²
Study Notes
Electric Charge
- Electric charge is a fundamental property of matter, denoted by the letter Q.
- There are two types of electric charges: positive (+) and negative (-).
- Like charges repel, unlike charges attract.
- An uncharged body has an equal number of protons and electrons.
Conductors and Insulators
- Conductors are substances that can carry electric charges, such as metals, which have free electrons.
- Insulators are substances that do not allow electric charges to move easily, such as rubber, plastic, and glass.
- Semi-conductors are materials that have properties of both conductors and insulators, examples include silicon and germanium.
Methods of Charging a Body
- Charging by friction: transferring electrons from one substance to another, resulting in a positively charged body (loses electrons) and a negatively charged body (gains electrons).
- Charging by induction: redistributing charges on a conductor when a charged body is brought close, but not touching.
- Charging by contact: sharing charges between two conductors, resulting in both bodies having the same sign of charge.
Electric Field and Lines of Electric Force
- Electric field is a region where an electric force is felt by a charged body, represented by electric lines of force.
- Electric field is a vector quantity with direction and magnitude.
- Direction of electric field is defined as the direction of the force on a small positive charge.
- Electric field strength or intensity is the magnitude of the electric field.
Law of Force Between Two Charges (Coulomb's Law)
- The force between two electrically charged bodies is inversely proportional to the square of the distance between them.
- The electric force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
- Formula: F = k * q1 * q2 / r^2, where k is a constant.
Permittivity and Relative Permittivity
- Permittivity is the ability of a material to store electric charge.
- Relative permittivity is the ratio of the material's permittivity to that of a vacuum.
- Formula: εr = ε / ε0.
Electric Field Strength or Electric Field Intensity
- Electric field strength is the force per unit charge, denoted by E.
- Formula: E = F / Q, where F is the force and Q is the charge.
- Unit of E is Newton per Coulomb (N/C) or Volt per meter (V/m).
Field Strength E due to a Point Charge
- Formula: E = k * q / r^2, where k is a constant, q is the charge, and r is the distance.
- In a vacuum, k = 4πε0, so E = 1 / (4πε0) * q / r^2.
This quiz covers the topics of forces in nature, electrostatics, Coulomb's law, and superposition, as part of a general physics II course.
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