High school physics electromagnetism all concept knowledge point formula (to be complete)

High school physics electromagnetism all concept knowledge point formula (to be complete)

10、 Electric field
1. Two kinds of charge, charge conservation law, elementary charge: (E = 1.60 × 10-19c); the charge quantity of charged body is equal to the integral multiple of elementary charge
2. Coulomb's Law: F = kq1q2 / R2 (in vacuum) {F: force between point charges (n), K: electrostatic constant, k = 9.0 × 109n &; m2 / C2, Q1, Q2: electric quantity of two point charges (c), R: distance between two point charges (m), direction on their connecting line, force and reaction, mutual repulsion of the same kind of charges, mutual attraction of different kinds of charges}
3. Electric field strength: e = f / Q (definition formula, calculation formula) {e: electric field strength (n / C), is vector (superposition principle of electric field), Q: electric quantity of inspection charge (c)}
4. The electric field formed by the vacuum point (source) charge e = KQ / r2 {R: the distance from the source charge to the position (m), Q: the electric quantity of the source charge}
5. The field strength of uniform electric field E = UAB / D { UAB:AB The voltage (V) between two points, D: the distance (m) of AB two points in the direction of field strength}
6. Electric field force: F = QE {F: electric field force (n), Q: electric quantity of electric charge (c), e: electric field intensity (n / C)}
7. Potential and potential difference: UAB = φ a - φ B, UAB = WAB / Q = - Δ EAB / Q
8. Work done by electric field force: WAB = quab = eqd {WAB: work done by electric field force when charged body is from a to B (J), Q: charge (c), UAB: potential difference between a and B in electric field (V) (work done by electric field force is independent of path), e: intensity of uniform electric field, D: distance between two points along the direction of electric field strength (m)}
9. Electric potential energy: EA = q φ a {EA: electric potential energy of charged body at point a (J), Q: electric quantity (c), φ A: electric potential at point a (V)}
10. Change of electric potential energy Δ EAB = eb-ea {difference of electric potential energy of charged body from a position to B position in electric field}
11. Work done by electric field force and change of electric potential energy Δ EAB = - WAB = - quab (the increment of electric potential energy is equal to the negative value of work done by electric field force)
12. Capacitance C = q / u (definition formula, calculation formula) {C: capacitance (f), Q: electric quantity (c), u: voltage (potential difference between two plates) (V)}
13. Capacitance of parallel plate capacitor C = ε s / 4 π KD (s: opposite area of two plates, D: vertical distance between two plates, ω: dielectric constant)
Common capacitors [see P111, Volume 2]
14. Acceleration of charged particles in electric field (VO = 0): w = Δ EK or Qu = mvt2 / 2, VT = (2qu / M) 1 / 2
15. Deflection of charged particles in the direction perpendicular to the electric field at the velocity VO into the uniform electric field (without considering the effect of gravity)
Quasi plane vertical electric field direction: uniform linear motion L = VOT (in parallel plates with equal amount of heterogeneous charges: e = u / D)
The throwing motion is parallel to the electric field direction: the uniformly accelerated linear motion with zero initial velocity d = at2 / 2, a = f / M = QE / m
Note:
(1) When two identical charged metal spheres are in contact, the distribution of electric quantity is as follows: those with different charges are neutralized first and then equally divided, and those with the same charges are equally divided;
(2) The electric field line starts from the positive charge and ends at the negative charge. The electric field line does not intersect, and the tangent direction is the direction of field strength. The electric field line is strong at the close position of the electric field line, and the electric potential is lower and lower along the electric field line, and the electric field line is perpendicular to the equipotential line;
(3) The electric field line distribution of common electric fields should be memorized [see Fig. [p98, Volume 2];
(4) The electric field strength (vector) and electric potential (scalar) are determined by the electric field itself, and the electric field force and electric potential energy are also related to the electric quantity of the charged body and the positive and negative charge;
(5) In electrostatic equilibrium, the conductor is an equipotential body, and the surface is an equipotential surface. The electric field line near the outer surface of the conductor is perpendicular to the surface of the conductor, and the combined electric field strength inside the conductor is zero. There is no net charge inside the conductor, and the net charge only distributes on the outer surface of the conductor;
(6) Capacitance unit conversion: 1F = 106 μ f = 1012pf;
(7) The electron volt (EV) is the unit of energy, 1eV = 1.60 × 10-19j;
(8) Other related contents: electrostatic shielding [see P101 in Volume 2] / oscilloscopes, oscilloscopes and their applications [see p114 in Volume 2] equipotential surface [see P105 in Volume 2]
11、 Constant current
1. Current intensity: I = q / T {I: current intensity (a), Q: electric quantity (c), t: time (s)}
2. Ohm's Law: I = u / R {I: current intensity of conductor (a), u: voltage at both ends of conductor (V), R: resistance of conductor (Ω)}
3. Resistance and resistance law: r = ρ L / s {ρ: resistivity (Ω & # 8226; m), l: conductor length (m), s: conductor cross-sectional area (M2)}
4. Ohm's law of closed circuit: I = E / (R + R) or E = IR + IR can also be e = u inside + U outside
{I: total current in the circuit (a), e: power supply electromotive force (V), R: external circuit resistance (Ω), R: power supply internal resistance (Ω)}
5. Electric work and electric power: w = uit, P = UI {W: electric work (J), u: voltage (V), I: current (a), t: time (s), P: electric power (W)}
6. Joule's Law: q = i2rt {Q: Electrothermal (J), I: current through conductor (a), R: resistance value of conductor (Ω), t: power on time (s)}
7. In pure resistance circuit: because I = u / R, w = q, w = q = uit = i2rt = u2t / R
8. Total power rate, power output power and power efficiency: P total = ie, P output = IU, η = P output / P total {I: total circuit current (a), e: power electromotive force (V), u: terminal voltage (V), η: power efficiency}
9. Series / parallel series circuit (P, u and R are proportional) and parallel circuit (P, I and R are inverse)
Resistance relation (series, parallel and reverse) R series = R1 + R2 + R3 + 1 / R parallel = 1 / R1 + 1 / r2 + 1 / R3+
Current relation I total = I1 = I2 = I3 I and = I1 + I2 + i3+
Voltage relation u total = U1 + U2 + U3 + U total = U1 = U2 = u3
Power distribution P total = P1 + P2 + P3 + P total = P1 + P2 + P3+
10. Measure resistance with ohmmeter
(1) Circuit composition (2) measurement principle
After the two probes are short circuited, adjust RO to make the pointer of the meter fully deviate
Ig＝E/(r+Rg+Ro)
After connecting the measured resistance Rx, the current through the meter is
IX = E / (R + RG + ro + Rx) = E / (r middle + Rx)
Because IX corresponds to Rx, it can indicate the measured resistance
(3) Usage: mechanical zero adjustment, range selection, Ohm zero adjustment, reading measurement {pay attention to gear (magnification)}, off gear
(4) Note: when measuring the resistance, disconnect from the original circuit, select the range to make the pointer near the center, and re short the ohm to zero for each shift
11. Measuring resistance by voltammetry
Ammeter internal connection method:
Voltage representation: u = ur + UA
Ammeter external connection method:
Current representation: I = IR + IV
The measured value of Rx = u / I = (UA + ur) / IR = RA + RX > r true
The measured value of Rx = u / I = ur / (IR + IV) = rvrx / (RV + R) > RA [or RX > (rarv) 1 / 2]
Select circuit condition RX