PHY102: General Physics II

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Questions and Answers

What is the symbol used to denote an electric charge?

Q (correct)

What is the result of like charges interacting with each other?

They cancel each other out

They repel each other (correct)

They have no effect on each other

They attract each other

What happens to the number of electrons in a body that is positively charged?

It remains the same

It decreases (correct)

It becomes zero

It increases

What is the purpose of rubbing a rod to charge it?

To transfer energy Signup and view all the answers

What is the result of unlike charges interacting with each other?

They attract each other Signup and view all the answers

What is a characteristic of an uncharged body?

It contains an equal number of protons and electrons Signup and view all the answers

What is the type of charge that a body has if it contains an excess of electrons?

Negative charge Signup and view all the answers

What is the primary method of conduction in metals?

Movement of free electrons Signup and view all the answers

What is the purpose of the fundamental law of action between charges?

To describe the interaction between like and unlike charges Signup and view all the answers

What type of materials do not allow electric charges to move easily through them?

Insulators Signup and view all the answers

What is the result of rubbing a glass rod with silk?

The glass rod becomes positively charged Signup and view all the answers

What occurs when a charged body is brought close to an uncharged body?

The redistribution of charges on the uncharged body occurs Signup and view all the answers

What type of materials share both the properties of conductors and insulators?

Semiconductors Signup and view all the answers

What is the result of charging a body by friction?

The body can be either positively or negatively charged Signup and view all the answers

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 Signup and view all the answers

What is the term for charging a body by rubbing two substances together?

Charging by friction Signup and view all the answers

What is the phenomenon of separation of charges in a conductor due to a nearby charged body known as?

Electrostatic induction Signup and view all the answers

What happens to a conductor when it is earthed momentarily while under the influence of a charged body?

It becomes permanently charged Signup and view all the answers

What is the result of charging a conductor by contact with another charged conductor?

The total charge remains the same Signup and view all the answers

What is the direction of an electric field at a point?

The direction of the force on a small positive charge Signup and view all the answers

Electric lines of force emanate from?

Positive charges Signup and view all the answers

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 Signup and view all the answers

What is the electric force between two point charges directly proportional to?

The product of the charges Signup and view all the answers

What is the electric field strength also known as?

Electric intensity Signup and view all the answers

What is the unit of charge in the S.I system?

Coulomb Signup and view all the answers

What is the formula for electric field strength E?

E = F/Q Signup and view all the answers

What is the direction of the electric field strength E?

The direction of the force on a positive charge Signup and view all the answers

What is the unit of electric field strength E?

Newton per Coulomb Signup and view all the answers

What is the relative permittivity of a medium?

The ratio of its material permittivity to that of a vacuum Signup and view all the answers

What is the formula for the relative permittivity of a medium?

εr = ε/ε0 Signup and view all the answers

What is the constant k in the formula F = kq1q2/r^2?

4πε0 Signup and view all the answers

What is the electric field defined as?

A region where an electric force is felt Signup and view all the answers

What is the practical unit of electric field strength?

Volt per metre (V m−1) Signup and view all the answers

What is the formula for the electric field strength due to a point charge?

E = kq / r² Signup and view all the answers

What is the value of k in the formula for electric field strength?

4πϵ₀ Signup and view all the answers

What is the direction of the net force acting on the +15C charge?

At an angle of 27.60° to the −20C charge Signup and view all the answers

What is the magnitude of the force of attraction between +15C and −20C?

3 × 10¹¹ N Signup and view all the answers

What is the magnitude of the net force acting on the +15C charge?

6.5 × 10¹¹ N Signup and view all the answers

What is the angle of the net force acting on the +15C charge?

27.60° Signup and view all the answers

What is the formula for the electric field strength at a point P due to two point charges?

E = k(q₁ + q₂) / r² Signup and view all the answers

What determines the direction of the magnetic field around a current-carrying conductor?

The right-hand thumb rule Signup and view all the answers

Which application is NOT associated with Biot-Savart's Law?

Determining voltage in a circuit Signup and view all the answers

What is similar to Biot-Savart Law in the context of electrostatics?

Coulomb's Law Signup and view all the answers

In the context of a circular coil, what parameter directly affects the magnetic field at its center?

The number of turns and current Signup and view all the answers

What condition must be met for Biot-Savart Law to be applicable?

The current distribution must be symmetrical Signup and view all the answers

How does the magnetic field behave at the center of a semicircular piece of wire?

It is determined by the current and radius Signup and view all the answers

What is the typical unit for measuring the magnetic field strength generated by a coil?

Tesla Signup and view all the answers

For a wire loop of radius R carrying current I, the direction of magnetic field is:

Perpendicular to the plane of the loop Signup and view all the answers

What does Biot-Savart's Law relate to?

The magnetic field produced by a current carrying segment. Signup and view all the answers

What is the formula for the magnetic field produced by a current element according to Biot-Savart's Law?

$B = rac{μ_0 i ds sin(θ)}{4πr^3}$ Signup and view all the answers

What is the value of μ0 in Biot-Savart's Law?

4π × 10^-7 TmA-1 Signup and view all the answers

What type of physical quantity is a current element (ids) in the context of Biot-Savart's Law?

Vector quantity Signup and view all the answers

Which law describes the relationship between electric current and magnetic fields?

Biot-Savart Law Signup and view all the answers

In Biot-Savart's Law, what does the variable 'r' represent?

Distance from the wire to the point of measurement Signup and view all the answers

What physical concept does the term 'permeability of free space' refer to?

The measure of how easily a magnetic field can penetrate a vacuum Signup and view all the answers

Which of the following is a direct application of Biot-Savart's Law?

Determining the magnetic field around a wire carrying current Signup and view all the answers

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.

Course Overview

Course Title: General Physics I (Mechanics)
Course Code: PHY 102
Credit Units: 2 C Units
Week 6 Lecturer: Dr. Adegbenro S. AJANI
Topics Covered: Magnetic fields, Lorentz force, Biot-Savart and Ampère's laws, Magnetic dipoles, Dielectrics, Energy in magnetic fields, and solved problems.

Course Objectives

Discuss the definition of a magnetic field.
State the Lorentz law and write the formula for Lorentz force.
Explain Biot-Savart and Ampère’s laws, including applications.
Discuss magnetic dipoles and dielectrics.
Solve problems involving energy in magnetic fields.

Biot-Savart Law

Relates magnetic fields to electric currents in electromagnetism.
Describes the magnetic field produced by a current-carrying segment, referred to as the current element.
Formula involves current element, distance vector, and angle:
[ B = \frac{\mu_0}{4\pi} \frac{I , ds \times \hat{r}}{r^2} ]
( \mu_0 ): Permeability of free space, ( 4\pi \times 10^{-7} , TmA^{-1} ).
The direction of the magnetic field is perpendicular to both the current element and position vector, determined using the right-hand thumb rule.

Applications of Biot-Savart Law

Enables calculation of magnetic fields at atomic or molecular levels.
Utilized in aerodynamic theories to compute velocity induced by vortex lines.

Importance of Biot-Savart Law

Analogous to Coulomb’s law in electrostatics.
Applicable for small current-carrying conductors.
Relevant for symmetrical current distributions.

Solved Problems on Biot-Savart Law

Magnetic Field of Wire Loop: Calculate at center of a circular loop with radius ( R ) and current ( I ).
Magnetic Field of Circular Coil: Coil with radius ( 5 \times 10^{-2} , m ) and 40 turns carrying ( 0.25 , A ) current.
Magnetic Field of Semicircular Wire: Radius of ( 0.20 , m ) with ( 150 , A ) current; calculate magnetic field at the center.

General Notes

Understanding magnetic fields is crucial for studying electromagnetic forces.
Mastery of key concepts such as Lorentz force, Biot-Savart law, and their applications is essential for solving problems in electromagnetism.

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Description

This quiz covers the topics of forces in nature, electrostatics, Coulomb's law, and superposition, as part of a general physics II course.

PHY102: General Physics II - Week 2

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