Charge | Coulombs | Elementary Charge |
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+1 | 1.602 × 10^-19 C | 1 e |
+2 | 3.204 × 10^-19 C | 2 e |
+3 | 4.806 × 10^-19 C | 3 e |
-1 | -1.602 × 10^-19 C | -1 e |
-2 | -3.204 × 10^-19 C | -2 e |
-3 | -4.806 × 10^-19 C | -3 e |
-1.602 x 10^-19 C
.F = k * (q1 * q2) / r^2
E = F / q
V = W / q
ΔV = V2 - V1
Electrostatic force is the force that exists between electrically charged particles. This force can be either attractive or repulsive, depending on the charges of the particles. The strength of the electrostatic force is determined by Coulomb's Law. The equation for calculating electrostatic force is:
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Coulomb's Law states that the electrostatic force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. The mathematical expression for Coulomb's Law is:
F = k * (q1 * q2) / r^2
Coulomb's constant is a proportionality constant that depends on the medium between the charged particles.
In a vacuum, Coulomb's constant has a value of approximately 9 x 10^9 N*m^2/C^2
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The electrostatic force between two charged particles can be attractive or repulsive, depending on the signs of their charges.
Like charges (positive and positive, or negative and negative) repel each other, while opposite charges (positive and negative) attract each other.
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Electric field strength is the force per unit charge experienced by a test charge placed in an electric field. It is a vector quantity and is denoted by E.
The electric field strength at a point in an electric field is given by the formula:
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The SI unit of electric field strength is newtons per coulomb (N/C).
The direction of the electric field strength is the direction of the force experienced by a positive test charge placed in the electric field.
E = k * Q / r^2
E = k * Q / r^2
E = k * Q * r / R^3
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Electric potential energy: It is the energy that a charged particle possesses due to its position in an electric field. It is defined as the amount of work required to move a charged particle from infinity to a point in the electric field.
The SI unit of electric potential energy is joule (J).
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V = kq/r
E = -∇V
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∮E⋅dA = Q/ε0
Flux is the amount of a physical quantity passing through a given surface.
In electrostatics, electric flux is the measure of the electric field passing through a given surface.
Mathematically, electric flux can be expressed as:
Φ = ∫E ⋅ dA
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A point charge of +2 nC is located at the center of a sphere of radius 10 cm. Find the electric flux through the surface of the sphere.
Solution
Φ = Q / ε₀
Q = +2 nC
E = kQ / r²
E = (9 × 10^9 Nm²/C²) × (2 × 10^-9 C) / (0.1 m)²
E = 36 N/C
Φ = E × A
A = 4πr²
A = 4π × (0.1 m)²
A = 0.04π m²
Φ = (36 N/C) × (0.04π m²)
Φ = 4.52 Nm²/C
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Line of Charge | ![]() |
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Point, Hoop, or Sphere | ![]() |
Sphere | ![]() |
Insulating Sheet of Charge | ![]() |
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C = Q/V
C = εA/d
E = V/d
U = (1/2)CV^2
E = 1/2 * C * V^2
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Material | Dielectric Constant (k) |
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Air | 1.0006 |
Vacuum | 1.0 |
Teflon | 2.1 - 2.3 |
Glass | 4.5 - 8.5 |
Water | 80.4 |
Diamond | 5.5 |
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V = I * R
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P = VI
P = VI
P = 12V x 2A = 24W
P = I^2R
or
P = V^2/R
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Example of KVL
+-----R1-----+
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V1 R3
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+-----R2-----+
V1 - V(R1) - V(R2) - V(R3) = 0
R_total = R1 + R2 + R3 + ... + Rn
1/R_total = 1/R1 + 1/R2 + 1/R3 + ... + 1/Rn
EMF stands for electromotive force and is the voltage generated by a battery or other source of electrical energy.
EMF Equation
The EMF of a battery is the maximum voltage that it can provide when no current is flowing through it.
The EMF of a battery is affected by factors such as temperature, the concentration of the electrolyte, and the materials used in the electrodes.
The EMF of a battery can be measured using a voltmeter connected across its terminals when no current is flowing through it.
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1/C_total = 1/C_1 + 1/C_2 + ... + 1/C_n
C_total = C_1 + C_2 + ... + C_n
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RC circuits are circuits that contain a resistor and a capacitor. These circuits are used in a variety of applications, including filters, timing circuits, and oscillators.
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Capacitor Charging
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Capacitor Discharging
When a charged capacitor is disconnected from a voltage source and connected to a resistor, it discharges through the resistor.
The time it takes for the capacitor to discharge to 36.8% of its initial voltage is given by the time constant.
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RC Filters
RC Oscillators
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The right hand rule is a mnemonic technique used to determine the direction of a magnetic field in relation to the direction of the current flowing through a wire.
How to use the right hand rule
The right hand rule is used in various applications, including:
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F = q(v x B)
F = qE
F = qE + q(v x B)
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F = I L x B
B_perp = B sin(theta)
T = F * r * sin(theta)
k = T / theta
When an electric current flows through a wire, it generates a magnetic field around the wire. This magnetic field can be visualized using magnetic field lines, which show the direction and strength of the magnetic field at different points around the wire.
The direction of the magnetic field around a current-carrying wire can be determined using the right-hand rule. If you point your right thumb in the direction of the current flow, the direction of the magnetic field lines can be determined by the direction your fingers curl around the wire.
The strength of the magnetic field around a current-carrying wire depends on the amount of current flowing through the wire and the distance from the wire. The magnetic field strength decreases as the distance from the wire increases.
A solenoid is a coil of wire that is wrapped around a cylindrical object, such as a metal rod. When a current flows through the wire, it generates a magnetic field that is concentrated inside the coil. The strength of the magnetic field can be increased by increasing the number of turns in the coil or by increasing the current flowing through the wire.
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F = μ₀I₁I₂L / 2πd
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The Biot-Savart Law is a fundamental law in electromagnetism that describes the magnetic field produced by a current-carrying wire. It was discovered by Jean-Baptiste Biot and Felix Savart in 1820.
The Biot-Savart Law states that the magnetic field at a point is proportional to the current density and the distance from the point to the current element. The direction of the magnetic field is perpendicular to both the current element and the vector from the current element to the point.
Mathematically, it is written as:
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The Biot-Savart Law is used to calculate the magnetic field produced by a current-carrying wire or a group of wires. It is also used in the calculation of the magnetic field of a solenoid, a toroid, and other complex geometries.
The Biot-Savart Law is only valid for steady currents and does not take into account the effects of changing electric fields. It also assumes that the current density is constant throughout the wire, which may not be the case in practice.
A long straight wire carries a current of 5 A. Find the magnetic field at a point 3 cm away from the wire.
Solution
B = (μ₀ * I)/(2πr)
B
is the magnetic field, I
is the current, r
is the distance from the wire, and μ₀
is the permeability of free space.B = (4π * 10^-7 * 5)/(2π * 0.03)
B = 3.33 * 10^-5 T
3.33 * 10^-5 T
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Ampère's Law is a fundamental law of electromagnetism that relates the magnetic field around a closed loop to the electric current passing through the loop. The law was discovered by André-Marie Ampère in 1826.
The law states that the line integral of the magnetic field around a closed loop is equal to the current passing through the loop multiplied by a constant known as the permeability of free space.
Mathematically, the law can be expressed as:
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A long, straight wire carries a current of 10 A. What is the magnetic field at a distance of 5 cm from the wire?
Solution
B * 2πr = μ0 * I
B * 2π(0.05) = 4π * 10^-7 * 10
B = 2 * 10^-6 T
Φ = B * A * cos(θ)
EMF = -dΦ/dt
ε = -dΦ/dt
L = NΦ/I
W = 1/2 * L * I^2
f = 1 / (2π√LC)
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Maxwell's equations are a set of four fundamental equations that describe the behavior of electric and magnetic fields.
Gauss's Law for Electric Fields
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Gauss's Law for Magnetic Fields
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There are no magnetic charges. Magnetic field lines always close in themselves.
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Faraday's Law of Electromagnetic Induction
This equation states that a changing magnetic field induces an electric field. In mathematical terms, it can be written as:
where
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Ampere's Law with Maxwell's Correction
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