High school physical electric field formula
1. Two kinds of charges, law of charge conservation and elementary charge: (e= 1.60? 10- 19C)； The charge of a charged body is equal to an integer multiple of elementary charge.
2. Coulomb's Law: F=kQ 1Q2/r2 (in vacuum) {F: the force between point charges (n), k: the electrostatic constant k=9.0? 109Nm2/C2, Q 1, Q2: the electric quantity of two charges (c), r: the distance between two charges (m), the direction is on their connection line, the acting force and reaction force, the same charges repel each other, and the different charges attract each other}
3. Electric field intensity: E=F/q (definition formula, calculation formula) {E: electric field intensity (N/C), which is a vector (electric field superposition principle), and q: the quantity of electric charge (c).
4. The electric field formed by the vacuum point (source) charge E=kQ/r2 {r: the distance from the source charge to this position (m), Q: the electric quantity of the source charge}
5. The field strength of uniform electric field E = UAB/D {Voltage between two points in the field strength direction (V)UAB:AB and the distance between two points (M)}
6. Electric field force: F=qE {F: electric field force (n/c)}, q: electric quantity of charge affected by electric field force (c), e: electric field strength (N/C)}
7. Potential and potential difference: UAB=? A-? b，UAB=WAB/q=-？ EAB/q
8. Work done by electric field force: WAB=qUAB=Eqd{WAB: Work done by electric field force when charged body goes from A to B (J), Q: Charged amount (C), UAB: potential difference (V) between points A and B in electric field (the work done by electric field force has nothing to do with the path), E: uniform electric field strength, and D: along the field strength direction.
9. electric potential energy: EA=q? A {ea: electric potential energy (j) of charged body at point A, Q: electric quantity (c),? A: potential at point a (v)
10. the change of electric potential energy? EAB = e B-EA {difference of electric potential energy of charged body from position A to position B in electric field}
1 1. What work did the change of electric field force and electric potential energy do? EAB =-WAB =- quart (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. the capacitance of parallel plate capacitor C=? S/4？ Kd(S: relative area of two plates, d: vertical distance of two plates,? : dielectric constant)
14. acceleration of charged particles in electric field (v0 = 0): w =? EK or qU=mVt2/2, Vt=(2qU/m) 1/2.
15. Deflection of charged particles when they enter a uniform electric field along a vertical electric field at the speed of V0 (regardless of gravity); Vertical electric field direction: uniform linear motion L=V0t, parallel electric field direction: uniform accelerated linear motion with zero initial velocity d=at2/2, a = f/m = QE/m.
High school physics constant current formula
1. current intensity: I=q/t{I: current intensity (a), q: the amount of electricity passing through the lateral load surface of the conductor in time t (c), t: time (s)}
2. Ohm's Law: I=U/R {I: conductor current intensity (a), u: voltage across the conductor (v), r: conductor resistance (? )}
3. Resistance and resistance law: R=? L/S{？ : resistivity (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: electromotive force of power supply (V), R: external circuit resistance (? ), r: internal resistance of power supply (? )};
5. Electric power and power: W=UIt, P=UI{W: electric power (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 (? ), t: power-on time (seconds)}; 7. In a pure resistance circuit: because I = u/r and W = q, because three, W = q = UIT = I2RT = U2T/r; 8. Total power activity, power output and power efficiency: P total =IE, P output =IU,? = pOutput/pTotal {I: total circuit current (a), e: electromotive force of power supply (v), u: terminal voltage (v),? : power efficiency}
9. Series/parallel series circuit of the circuit (P, U is proportional to R) Parallel circuit (P, I is inversely proportional to R)
Resistance relation (series-same-parallel-opposite) r series = r1+R2+R3+1/rparallel =1/r1+/R3+
The current relation I is always =I 1=I2=I3 I and =I 1+I2+I3+
The voltage relationship utotal = u1+U2+u3+utotal = u1= U2 = u3.
Power distribution Ptotal = p1+P2+P3+Ptotal = p1+P2+P3+
10. measuring resistance with ohmmeter: (1) circuit composition (2) measuring principle
After the two probes are short-circuited, adjust R0 to make the instrument pointer full of bias, and get IG = E/(R+RG+R0); After connecting the measured resistor Rx, the current through the meter is
IX = E/(R+Rg+R0+Rx)= E/(R+Rx)； Because Ix corresponds to Rx, it can represent the measured resistance.
(3) Usage: mechanical zero adjustment, range selection, ohm zero adjustment, measurement reading (pay attention to gear (amplification)) and gear off.
(4) Note: When measuring the resistance, disconnect it from the original circuit, select the measuring range so that the pointer is near the center, and re-short the ohm to zero in each gear.
1 1. Voltammetry to measure resistance.
Internal connection of ammeter: voltage expression: u = ur+ua; External connection of ammeter: current expression: I=IR+IV.
RX =U/I=(UA+UR)/R=RA+RX > measured value; R is true; RX = u/I = ur/(IR+iv) = rvrx/(RV+r) measured value.
Select the circuit condition Rx>& gtRA[ or rx> (rarv)1/2]; Select circuit condition rx
12. Current limiting connection and voltage dividing connection of sliding rheostat in the circuit;
Current-limiting connection: the voltage adjustment range is small, the circuit is simple, the power consumption is low, and it is convenient to adjust the voltage selection condition RP >；; Prescription (abbreviation for prescription)
Voltage-dividing connection: wide voltage adjustment range, complex circuit, large power consumption, and convenient adjustment of voltage selection condition RP.
Knowledge points of physics and electricity in senior high school
First, the basic law of electric field
1, law of conservation of charge: charge will neither be created nor destroyed, but it can only be transferred from one object to another, or from one part of an object to another, and the total amount of charge remains unchanged during the transfer process. (1) Three charging modes: friction charging, induction charging and contact charging.
(2) Meta-charge: the smallest charged unit. The charge of any charged body is an integer multiple of meta-charge, e= 1.6? 10- 19C Millikan measured the value of e.
2. Coulomb's Law
Law content (1): The interaction force between charges at two stationary points in vacuum is directly proportional to the product of their charges and inversely proportional to the square of their distance, and the direction of the interaction force is on their connecting line.
(2) Expression: k=9.0? 109N？ M2/C2 electrostatic force constant
(3) Applicable conditions: static point charge in vacuum.
Second, the nature of electric field energy
1, the basic property of electric field energy: the charge moves in the electric field, and the electric field force should do work on the charge.
2. potential?
(1) Definition: the ratio of the potential energy Ep of a point charge in an electric field to the amount of charge.
(2) Definition:? Unit: Volts (V) Signed calculation.
(3) Features:
○ 1 potential is relative, relative to the reference point. But the difference of potential has nothing to do with the choice of reference point.
○2 potential is scalar, but it has positive and negative sign. The sign only indicates whether the potential at this point is higher or lower than that at the reference point.
○3 The electric potential is determined by the electric field itself and has nothing to do with Ep and Q. ..
○4 The potential is numerically equal to the work done by the electric field force when the unit positive charge moves from this point to the zero potential point.
(4) the method of judging the potential level
○ 1 According to the electric field line, the potential decreases along the electric field line. ? A & gt？ B
2 According to the electric potential energy:
Positive charge: large potential energy and high potential; Small potential energy, low potential.
Negative charge: large potential energy and low potential; Small potential energy, high potential.
Conclusion: Only under the action of electric field force can electrostatic charge move from the place with high electric potential energy to the place with low electric potential energy.
3. Potential energy Ep
(1) Definition: Due to the interaction between electric field and charge, the energy of charge in electric field is determined by its position. The electric potential energy of a charge at a certain point is equal to the work done by the electric field force to move the charge from that point to the zero potential energy position.
(2) Definition formula: signed calculation
(3) Features:
○ 1 electric potential energy is relative. Relative to the zero potential energy surface, the earth or the zero potential energy surface at infinity is usually selected.
○2 The change of electric potential energy △Ep has nothing to do with the choice of zero potential energy surface.
4. Potential difference UAB
(1) Definition: potential difference between two points in an electric field. Also known as voltage.
(2) Definition: UAB=? A-? B
(3) Features:
○ 1 potential difference is scalar, but it has a sign, and the sign only indicates who has higher or lower potential at the starting point and the end point. If UAB>；; 0, then UBA.
2 units: Volts
○3 The potential difference between two points in the electric field is certain and has nothing to do with the choice of zero potential plane.
○4U=Ed formula for calculating potential difference between two points in uniform electric field. Relationship between potential difference and electric field strength.
5, electrostatic equilibrium state
(1) Definition: The charge in a conductor has no steady state of directional motion.
(2) Features
○ 1 The internal field strength of the conductor in electrostatic balance is zero everywhere.
○2 The electric field generated by the induced charge at any position in the conductor is equal to and opposite to the external electric field there.
3 The whole conductor in electrostatic balance is an equipotential body, and the surface of the conductor is an equipotential surface.
○4 The charge is only distributed on the outer surface of the conductor, and the distribution of the conductor surface is related to the bending degree of the conductor surface. The more bends, the more charge distribution.
High school physics learning methods
Emphasize learning physics with hands and brains.
Physics is an experimental science. In physics teaching, we should attach importance to experiments, especially demonstration experiments and student experiments. Demonstration experiments must create conditions, be as open as possible, and pay attention to guiding students to observe. For students' experiments, we must emphasize that everyone should do it, not not not do it? Audience? ; Arrange some small experiments and small productions after class to cultivate students' practical ability. In class, on the basis of emphasizing concentration, each student is required to have a draft book, which is convenient for calculation and analysis on the draft paper during class, so as to use both hands and brains during class. When solving problems, let students develop the habit of sketching while thinking, and improve their ability to analyze with graphics, images and block diagrams.
Learn to understand and summarize.
Most girls work hard after entering high school, and they all have good wishes at the beginning of their studies, but they often get twice the result with half the effort, mainly because of the method. Good learning methods are the key to learning physics well. In the study of concepts and laws, we should pay attention to the connection of knowledge. The understanding of concepts, including the definition, nature, unit and relationship with other physical quantities, as well as the discovery of laws, content, scope of application and how to use them, needs to be understood. After class, we should do some exercises to consolidate knowledge, pay attention to the application of independent thinking and various creative thinking, find out the reasons for the mistakes in the exercises, make up for them in time and improve them. This also applies after the exam, so that you can get a score of 100 after the exam. When reviewing, the teacher should teach the girls to summarize, take the thick books lightly, sort out the main lines of knowledge, make the knowledge clear and achieve mastery through a comprehensive study. Pay attention to the induction and collection of the same type of questions and error-prone questions in exercises and tests to facilitate review. Teachers improve girls' learning ability by guiding them to learn the law, and girls' self-confidence will be greatly enhanced when they succeed in learning, forming a virtuous circle of learning.
Attach importance to the training of divergent thinking
Divergent thinking is a form of creative thinking. Different thinking directions are helpful to overcome the shortcomings of rigid and narrow thinking of girls for many years. ? How to solve a problem? 、? Ask more questions? 、? Think about one more question? It is a good way to train divergent thinking; In classroom teaching, examples with multiple solutions to one problem should be clearly explained and arranged after class; For open exercises with known conditions and unknown physical process, we should analyze the possibility of various scenarios with our classmates, explain the reasons for these scenarios and the methods of thinking, and consciously cultivate the thinking of revealing various possibilities through sketching.