All formulas of magnetic field

All formulas of magnetic field

Common formulas of Electromagnetics
Coulomb's Law: F = kqq / R & # 178;
Electric field strength: e = f / Q
Electric field intensity of point charge: e = KQ / R & # 178;
Uniform electric field: e = u / D
Electric potential energy: e & # 8321; = q φ
Potential difference: U &; &; = φ &; - φ &;
Work done by electrostatic force: W & # 8321; &# 8322; = Qu & # 8321; &# 8322;
Definition of capacitance: C = q / u
Capacitance: C = ε s / 4 π KD
Motion of charged particles in uniform electric field
Accelerating uniform electric field: 1 / 2 * MV & # 178; = Qu
v² =2qU/m
Deflection uniform electric field:
Exercise time: T = x / V & # 8320;
Vertical acceleration: a = Qu / MD
Vertical displacement: y = 1 / 2 * at & # 8322; = 1 / 2 * (Qu / MD) * (x / V & # 8320;), # 178;
Deflection angle: θ = V ⊥ / V ᦉ 8320; = qux / MD (V ᦉ 8320;), ᦉ 178;
Micro current: I = NESV
Non electrostatic work of power source: w = ε Q
Ohm's Law: I = u / R
Series circuit
Current: I &; = I &; = I &; =
Voltage: u = u &? 8321; + U &? 8322; + U &? 8323; +
Parallel circuit
Voltage: U &? 8321; = u &? 8322; = u &? 8323; =
Current: I = I &; + I &; + I &; +
Resistance series: r = R &; + R &; + R &; +
Resistance parallel connection: 1 / r = 1 / R &? 8321; + 1 / R &? 8322; + 1 / R &? 8323; +
Joule's Law: q = I & # 178; RT
P=I² R
P=U² /R
Electric power: w = uit
Electric power: P = UI
Resistance law: r = ρ L / S
Ohm's law of the whole circuit: ε = I (R + R)
ε = u outside + U inside
Ampere force: F = ilbsin θ
Magnetic flux: Φ = BS
electromagnetic induction
Induced electromotive force: e = n Δ Φ / Δ t
Magnetic induction line of wire cutting: Δ s = LV Δ t
E=Blv*sinθ
Induced electromotive force: e = l Δ I / Δ t
General arrangement of electromagnetics formula in senior high school physics
The electron charge is Coulomb (coul), 1coul = electron charge
1、 Electrostatics
1. Coulomb's law, which describes the electric power between two charges in space
,
Gauss's law of electric field can be deduced from Coulomb's law
2. The electric field formed by a point charge or a uniformly charged sphere in space
,
The tangent direction of power line is the direction of electric field. The denser the power line is, the stronger the electric field is
Electric field between parallel plates
3. The potential energy between a point charge or a uniformly charged sphere
4. The potential formed by a point charge or a uniformly charged sphere in space
The internal potential of the conductor is equal. The potential of the grounded conductor is zero
Where the potential is zero, the electric field may not be equal to zero
In a uniform electric field, the potential difference between two points is d. therefore, the potential difference between parallel plates
5. Capacitance is a component for storing charges. The larger the C is, the larger the amount of charges that can be stored under a fixed potential difference will be. The capacitance itself is electrically neutral, and the charges of + Q and - Q are stored on each pole. The capacitance stores electric energy at the same time
a. The capacitance of a spherical conductor, the other pole of which is infinite, has a charge of - Q
b. Therefore, in order to increase the capacitance, we must increase the plate area a, reduce the distance d between plates, or change the dielectric between plates to make K smaller
2、 Circuit Science
1. The potential difference between the two ends of the ideal battery is fixed as. The actual battery can be simplified as an ideal battery series internal resistance R. when the actual battery is discharging, the output voltage of the battery is limited, so the maximum output current is limited, and the maximum output voltage is equal to the electromotive force, which occurs when the output current is 0
When the actual battery is charging, the input voltage of the battery must be greater than the electromotive force
2. If the potential difference between two ends of a uniform conductor of length d is, then the internal electric field. There is no charge accumulation on the conductor, and the total charge is zero, so there is no electric field outside the conductor. There is no potential drop on the ideal conductor, so the internal electric field is equal to 0
3. Kirchhoff's law
a. Node theorem: the current flowing in at any point of the circuit is equal to the current flowing out
b. Loop theorem: the total potential rise equals the total potential drop in any loop of a circuit
3、 Magnetostatics
1. Biot Savart law, which describes the magnetic field created by a long wire in a place
, ,
The MKS system is Tesla, CGS system is Gauss, 1tesla = 10000 Gauss, the surface magnetic field is about 0.5 Gauss, which points from the south pole to the North Pole
Ampere's law can be deduced from Biot Savart's law
2. Important magnetic field formula
Magnetic field in solenoid with long magnetic field of infinite straight wire
The magnetic field produced by the coil of radius a on the axis X
The magnetic field at the center of the circle (x = 0) is
3. The magnetic force of the long current carrying wire is, when it is perpendicular to B
When the current direction is the same, the wires attract each other; when the current direction is opposite, the wires repel each other
4. The torque of the coil in the motor, where a is the area vector, the size is the coil area, and the direction is the normal vector of the coil surface, which is determined by the current direction and the right-hand rule
5. The magnetic force of charged particle in magnetic field is,
a. If the initial velocity of the particle is parallel to the magnetic field B, the particle moves with equal velocity and the trajectory is a straight line
b. If the initial velocity of the particle is perpendicular to the magnetic field B, the particle moves in a circle with equal velocity, and the trajectory is circle, radius of gyration and period
c. If there is an angle between the initial velocity of the particle and the magnetic field B, the particle moves in a spiral. The velocity component parallel to the magnetic field does not change in size and direction, while the velocity component parallel to the magnetic field does not change in size but in direction, and moves in an equal speed circular motion. The radius of gyration, period, and pitch are the same as those of B
Velocity selector: let the charged particle pass through the space perpendicular to the magnetic field and the electric field, then the force is zero and the particle moves at the same speed
The basic principle of the mass spectrometer is to use the velocity selector to fix the velocity of ions, and then drive the ions of the same element into a uniform magnetic field, measure the collision position, calculate the radius of gyration, and obtain the mass of ions
6. Gauss's law of magnetic field, that is, the magnetic flux on the closed surface must be zero, which means that the magnetic line of force must be closed and there is no magnetic monopole. The magnetic line of force outside the magnet starts from the N pole and ends at the S pole, and the magnetic line inside the magnet starts from the S pole and ends at the N pole
4、 Induced electromotive force and electromagnetic wave
1. Faraday's Law: induced electromotive force. Note that this is not to calculate the magnetic flux on a closed surface
The direction of the induced current caused by the induced electromotive force will make the magnetic force on the coil opposite to the direction of the external force
2. The induced electromotive force at both ends of the wire when the length of the wire cuts the magnetic line of force at the speed of V. if V, B, are perpendicular to each other, then
3. Faraday's law provides the method of converting mechanical energy into electrical energy, that is, the basic principle of generator. The electromotive force output by generator rotating at frequency f, the maximum induced electromotive force
The transformer is used to change the voltage of alternating current. There is no potential difference at the output when direct current is applied
It is also ideal that the transformer will not consume energy, which is conserved by energy
4. In the middle of the 19th century, Maxwell studied electromagnetism and obtained four formulas: 1
a. Gauss law of electric field
b. Faraday's law
c. Gauss law of magnetic field
d. Ampere's law
Maxwell modified Ampere's law from Faraday's law that changing magnetic field will produce electric field
e. Maxwell's modified Ampere's law is
a. , B., C. and modified E. are called Maxwell's equations, which are the basic equations of electromagnetism. Based on Maxwell's equations, the existence of electromagnetic wave and its propagation velocity are predicted
At the end of the 19th century, Hertz discovered the existence of electromagnetic wave
Lorenz force