Electrical formula and explanation in Physics I'm in the second grade of junior high school. The chapter of voltage before the monthly exam is OK, but the electric power behind is not,

Electrical formula and explanation in Physics I'm in the second grade of junior high school. The chapter of voltage before the monthly exam is OK, but the electric power behind is not,

As a physical quantity indicating the speed of electric energy consumption, the power of a consumer is equal to the electric energy consumed in one second. If the electric energy consumed in such a long period of time as "t" is "W", then the electric power of the consumer is p = w / T (definition). The electric power is equal to the product of voltage and current [1] (P = u · I)
Current = charge / time (SEC)
Electric work = current * voltage * time (seconds)
Electric power = electric power / time (seconds) = current * voltage
Series circuit:
Total voltage = voltage at both ends of conductor a + voltage at both ends of conductor B +
Total current = current through conductor a = current through conductor B =
Total resistance = resistance of conductor a + resistance of conductor B +
Parallel circuit:
Total voltage = voltage at both ends of conductor a = voltage at both ends of conductor B =
Total current = current through conductor a + current through conductor B
Current = charge / time (SEC)
Electric work = current * voltage * time (seconds)
Electric power = electric power / time (seconds) = current * voltage
Series circuit:
Total voltage = voltage at both ends of conductor a + voltage at both ends of conductor B +
Total current = current through conductor a = current through conductor B =
Total resistance = resistance of conductor a + resistance of conductor B +
Parallel circuit:
Total voltage = voltage at both ends of conductor a = voltage at both ends of conductor B =
Total current = current through conductor a + current through conductor B +
Reciprocal of total resistance = reciprocal of resistance of conductor a + reciprocal of resistance of conductor B +
Ohm's Law:
Current = voltage / resistance
Joule's Law:
Heat generated by conductor = current * voltage * time (seconds) closed
Find all physics electric formulas in junior high school
[electrical part]
1. Current intensity: I = q electric quantity / T
2. Resistance: r = ρ L / S
3. Ohm's Law: I = u / R
4. Joule's Law:
(1) , q = i2rt universal formula)
(2) , q = uit = Pt = UQ, electric quantity = u2t / R (pure resistance formula)
5. Series circuit:
（1）、I＝I1＝I2
（2）、U＝U1＋U2
(3) R = R1 + R2 (1), w = uit = Pt = UQ (universal formula)
(2) W = i2rt = u2t / R (pure resistance formula)
6. Parallel circuit:
（1）、I＝I1＋I2
（2）、U＝U1＝U2
（3）、1/R＝1/R1＋1/R2 [ R＝R1R2/(R1＋R2)]
(4) I1 / I2 = R2 / R1 (shunt formula)
（5）、P1/P2＝R2/R1
7 constant resistance:
（1）、I1/I2＝U1/U2
（2）、P1/P2＝I12/I22
（3）、P1/P2＝U12/U22
8 electric power:
(1) , w = uit = Pt = UQ (universal formula)
(2) W = i2rt = u2t / R (pure resistance formula)
9 electric power:
(1) , P = w / T = UI (universal formula)
(2) , P = I2R = U2 / R (pure resistance formula)
（2）、U＝U1＋U2
（3）、R＝R1＋R2
(4) U1 / U2 = R1 / R2 (partial pressure formula)
（5）、P1/P2＝R1/R2
In fact, you don't have to ask others to give you the ready-made ones. You will have a deep memory when you summarize them. You can copy down all the formulas of electricity in grade 2 of junior high school, and then convert the deformation formulas of each formula by yourself. Then, you can combine the relationship between each formula and list new formulas. It will be easier to solve problems. For example, P = UI, u = IR, so it will be transformed into P = I (square) r, and w = Pt, Therefore, it becomes w = I (square) RT. it is also suggested that you list the specific units of each formula and each quantity. The units must be unified. Physics needs to be studied by yourself. Only in this way can you learn better. I wish you good results in the exam! Please adopt
In fact, you don't have to ask others to give you the ready-made ones. You will have a deep memory when you summarize them. You can copy down all the formulas of electricity in grade 2 of junior high school, and then convert the deformation formulas of each formula by yourself. Then, you can combine the relationship between each formula and list new formulas. It will be easier to solve problems. For example, P = UI, u = IR, so it will be transformed into P = I (square) r, and w = Pt, Therefore, it becomes w = I (square) RT. it is also suggested that you list the specific units of each formula and each quantity. The units must be unified. Physics needs to be studied by yourself. Only in this way can you learn better. I wish you good results in the exam! Please accept, thank you! Mobile phone pure hand! Question: I'm a sophomore in high school. I can't find any books before. Now it's urgent to learn electricity
On the application of Q formula
A resistance wire of the electric heater in the home circuit is fused. It is fused not long after it is connected. Please analyze what's the matter? Why?
Which formula should we use? Q = i2rt? Or q = u2t / R? When should we use another formula? If we answer well, we will not break our promise
Lihewei's "it doesn't take long to fuse after connecting" is because the resistance wire becomes thicker after connecting, and then the resistance becomes smaller 19920125. But this is in the home circuit, u doesn't change. Does it have nothing to do with u? Ha ha, if everything is given in the title? It's not practical
This ah, I will, I am the representative of physics class in our class. In fact, there are many reasons. The simplest way to explain is as follows! According to the formula, q = U2 / RT, close the key instantly, use the resistance of the electrical appliance to prevent the very low resistance. The heat generated by the low resistance of q = U2 / RT and constant voltage will fuse the filament again
A complete collection of electrical formulas in junior high school physics
Junior high school physics electricity Formula 1 current intensity: I = q electric quantity / T 2 resistance: r = ρ L / S 3 Ohm law: I = u / R 4 Joule Law: 1 Q = i2rt universal formula) 2 q = uit = Pt = UQ electric quantity = u2t / R (pure resistance formula) 5 series circuit: 1 I = I1 = I2 2 u =
Junior high school physics electricity formula
1 current intensity: I = q electric quantity / T
2 resistance: r = ρ L / S
Ohm's Law: I = u / R
4 Joule's law
(1) q = i2rt universal formula)
(2) q = uit = Pt = UQ, electric quantity = u2t / R (pure resistance formula)
5 series circuit:
　　⑴I＝I1＝I2
　　⑵U＝U1＋U2
　　⑶R＝R1＋R2
(4) U1 / u... Deployment
Junior high school physics electricity formula
1 current intensity: I = q electric quantity / T
2 resistance: r = ρ L / S
Ohm's Law: I = u / R
4 Joule's law
(1) q = i2rt universal formula)
(2) q = uit = Pt = UQ, electric quantity = u2t / R (pure resistance formula)
5 series circuit:
　　⑴I＝I1＝I2
　　⑵U＝U1＋U2
　　⑶R＝R1＋R2
(4) U1 / U2 = R1 / R2 (partial pressure formula)
　　⑸P1/P2＝R1/R2
6 parallel circuit:
　　⑴I＝I1＋I2
　　⑵U＝U1＝U2
　　⑶1/R＝1/R1＋1/R2 [ R＝R1R2/(R1＋R2)]
(4) I1 / I2 = R2 / R1 (shunt formula)
　　⑸P1/P2＝R2/R1
7 constant resistance:
　　⑴I1/I2＝U1/U2
　　⑵P1/P2＝I12/I22
　　⑶P1/P2＝U12/U22
8 electric power:
(1) w = uit = Pt = UQ (universal formula)
(2) w = I ^ 2rt = u ^ 2T / R (pure resistance formula)
9 electric power:
(1) P = w / T = UI (universal formula)
(2) P = I2 ^ R = u ^ 2 / R (pure resistance formula)
P = u2i (for pure resistance parallel circuit)
Joule's Law: (when the circuit is pure resistance circuit, q = w) home circuit trunk current: I = P / u
Looking at the name plate for the normal working current of the appliance: I = P / u looking at the name plate for the resistance: r = U2 / P
Series circuit: I = I1 = I2, u = U1 + U2, r = R1 + R2 (r = NR0)
Parallel circuit: I = I1 + I2, u = U1 = U2 (pure parallel circuit)
Common (for simultaneous series or parallel circuits): w = W1 + W2, P = P1 + P2, put away
Basic formula
Note: we try to write down the words of the formula, not just the letters!
1. Ohm's Law:
Current=
(deformation formula: u = IR, i.e. voltammetric resistance principle)
2. Electric power: how fast the current works (consumes electric energy). The higher the electric power is, the brighter the bulb is. ... unfold
Basic formula
Note: we try to write down the words of the formula, not just the letters!
1. Ohm's Law:
Current=
(deformation formula: u = IR, i.e. voltammetric resistance principle)
2. Electric power: how fast the current works (consumes electric energy). The higher the electric power is, the brighter the bulb is.
A. (note that the two sets of units should not be confused with form 8.21)
B. Electric power = voltage × current p = UI
Note: there are only the above three basic formulas of electricity, the others are all derived formulas, that is to say, you can use these three formulas to do all the questions, but the process is a little complicated
(formula of electric power:)
3. Electric power, electric energy:
So w = Pt
(for example, 8.21:5)
(use an energy meter to measure the power of electrical appliances, and pay attention to the unit conversion into a unified one)
4. Electrothermal: I'll study after the mid-term exam, but not in the mid-term
Heat = square of current x resistance x time
In pure resistance circuit (such as electric lamp, electric heater, etc.), that is, the work done by current (consumed electric energy) is all converted into heat energy
Electric work (electric energy) = electric heating w = q can be deduced: q = Pt
Note: when applying the formula, note: all the above formulas are only applicable to the same circuit, but not to different circuits
Characteristics of series parallel circuit
First of all, we should learn to distinguish between series circuit and parallel circuit. Judgment method: look at the current path. If there is only one current path, it is in series; if there are two or more current paths, it is in parallel.
Features of series parallel circuit:
Series circuit
Parallel circuit
Current relation
In a series circuit, the current is equal everywhere
I = I1 = I2
In a parallel circuit, the total current is equal to the sum of the currents of each branch
I = I1＋I2
Voltage relation
The voltage at both ends of the series circuit is equal to the sum of the voltages at both ends of each part of the circuit
U = U1＋U2
In parallel circuit, the voltage at both ends of each branch is equal
U = U1 = U2
Resistance relation
The total resistance of a series circuit is equal to the sum of the series resistances
R = R1＋R2
The reciprocal of the total resistance of the parallel circuit is equal to the sum of the reciprocal of the parallel resistance
Law of distribution
In a series circuit, the voltage at each end of a resistor is proportional to its resistance
U1：U2 = R1：R2
In a parallel circuit, the current of each resistor is inversely proportional to its resistance
I1：I2 = R2：R1
Generalization of the above characteristics
Inferring the extension of the formula for calculating the total resistance of a and parallel circuits
When there are only two resistors, the above formula can be changed into: (most commonly used, junior high school stage, the resistance is basically no more than two)
When the resistances are of the same size, the above formula can be reduced to: (n is the number of resistances in parallel)
Infer the relationship between voltage, electric power, electric work, electric heat and resistance in series circuit
That is, in the series circuit, in addition to the current is equal everywhere, the voltage, electric power, electric power, electric heating and resistance are proportional
In parallel circuit, the relationship between voltage, electric power, electric power, electric heating and resistance is as follows
That is to say, in the parallel circuit, except that the voltage at both ends of each branch is equal, the current, electric power, electric work, electric heat and resistance are inversely proportional
Tips for solving problems
1. A series circuit means that the current is equal everywhere, so if you can find the current, you need to find it first. Current is the link between the various electrical appliances.
2. Parallel circuit means that the voltage of each branch is equal, so the voltage can be calculated first. Voltage is the link between the electrical appliances.
3. From the above generalization, we can see that the quantity related to electricity is related to the resistance (ratio)