The distribution law of resistance, current, voltage, electric power, electric power and electric heat in series and parallel circuits‘

The distribution law of resistance, current, voltage, electric power, electric power and electric heat in series and parallel circuits‘

1. Electric quantity: (1) definition: the quantity of electric charge in an object is called electric quantity, which is indicated by the symbol "Q"
(2) Unit: Coulomb, indicated by the symbol "C"
(3) Inspection: electroscope (structure, principle, use)
2. Current: (1) definition: the electric quantity passing through the cross section of conductor in one second is called current intensity (current). It is indicated by the symbol "I"
(2) Formula: I = q / T (definition formula), where I is the current intensity (current), q is the electric quantity passing through the cross section of conductor, and t is the power on time
(3) Unit: international unit - ampere (a). Other common units are ma and μ a
(4) Measurement: ammeter
(5) Circuit features: in series circuit, the current is equal everywhere, that is: I1 = I2 = I3 = =In
The sum of the currents in the parallel branches is equal to I2 + of the total currents in the parallel circuits +In
3. Voltage: (1) function of voltage: voltage is the cause of free charge directional movement to form current. It is indicated by the symbol "U"
(2) But the electric energy is converted into other forms of power supply by the conductor
(3) Unit: international unit - volt (V). Other commonly used units are kilovolt (kV), millivolt (MV) and microvolt (μ V)
(4) Several voltage values: 1. The voltage of a dry cell is u = 1.5 v
2. The voltage of each lead-acid battery is u = 2V
3. The voltage of lighting circuit (home circuit) is u = 220 v
4. The safe voltage to human body shall not be higher than 36 V (U ≤ 36 V)
(5) Measurement: voltmeter
(6) Circuit features: the total 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. That is, u = U1 + U2 + +Un
In a parallel circuit, the voltages at both ends of each branch are equal =Un
4. Resistance: (1) definition: the resistance of conductor to current is called resistance. It is indicated by the symbol "R"
(2) Unit: international unit - ohm (Ω). Other commonly used units are kiloohm (K Ω) and megaohm (m Ω)
(3) Factors determining the resistance: the resistance of a conductor is a property of itself. Its size depends on the length, cross-sectional area and material of the conductor. The resistance of the conductor is also related to the temperature
(4) Measurement: voltammetry (voltmeter and ammeter)
(5) Equivalent resistance: a. the total resistance of the series circuit is equal to the sum of the resistances of the series conductors +RN if all resistances are R, then r = Nr
b. The reciprocal of the total resistance of the parallel circuit is equal to the sum of the reciprocal of each parallel resistance +1/Rn
If the resistance of each parallel conductor is r, then 1 / r = n / R is r = R / n
5. Electric work: (1) definition: the work done by a current through a certain circuit is called electric work, which is represented by the symbol "W"
(2) Essence: the process of current doing work is essentially the process of converting electric energy into other forms of energy. How much work the current does, how much electric energy will be converted into other forms of energy, and how much electric energy will be consumed
(3) Unit: international unit - Joule (joule) (J)
Other units - kilowatt hour (KWH), also used in life "degree" to express
(4) Formula: definition formula - w = uit = Pt derivation formula - w = i2rt w = (U2 / R) t w = UQ (Q refers to electric quantity here)
(5) Measurement: measure with watt hour meter. Master its reading method (the last digit is decimal)
The name plate of the electric energy meter usually has the following contents: "220 V" - indicating that the rated voltage of the electric energy meter is 220 v
"5A" means that the maximum current allowed by the meter is 5 a
"Kwh" -- unit of electric work, namely "degree" and "3000r / kWh" -- means that for every kilowatt hour consumed, the turntable of the electric energy meter turns 3000 revolutions
(6) Electric power characteristics:
a. Electric power characteristics: in series circuit and parallel circuit, the total work done by the current is equal to the sum of the work done by the electric current of each part, that is, wtotal = W1 + W2
b. The work done in the circuit is proportional to the resistance in series
c. Electric power distribution relationship in parallel circuit: in parallel circuit, the work done by current through each resistor is inversely proportional to its resistance, that is, W1: W2 = R2: R1
6. Electric power: (1) definition: the work done by the current in unit time is called electric power. It is indicated by the symbol "P". Meaning: it is the physical quantity that indicates the speed of work done by the current
(2) Unit: international unit - watt (watt) (W). The other commonly used unit is kilowatt (kw)
(3) Formula: definition formula - P = w / T determinant - P = UI (because w = uit = PT) derivation formula - P = U2 / r = I2R (because P = UI, I = u / R, u = IR)
(4) Volt ampere and stopwatch can also be used to measure energy
(5) Rated power and actual power: the rated voltage and rated power are usually marked on the electric appliance's nameplate. For example, if a lamp is marked with "pz220-60", "220V 60W", you should know how to calculate R (because P = U2 / R, r = U2 / P), and also calculate the current I (because P = UI, I = P / U) when the lamp works normally. The brightness of the lamp depends on its actual power
(6) Electric power characteristics:
a. Characteristics of electric power: the total power consumed by series circuit and parallel circuit is equal to the sum of the power consumed by various electrical appliances, that is, P total = P1 + P2
b. The relationship between electric power and resistance in series circuit: the power consumed by each electrical appliance (resistance) in series circuit is directly proportional to its resistance, that is, P1 / P2 = R1 / R2
c. The relationship between electric power and resistance in parallel circuit: the power consumed by each electrical appliance (resistance) in parallel circuit is inversely proportional to its resistance, that is, P1 / P2 = R2 / R1
7. Electrothermal: (1) definition: the heat generated by the current passing through the conductor is called electrothermal, that is, the thermal effect of the current. It is represented by the symbol "Q"
(2) Unit: international unit - Joule (joule) (J)
(3) Formula: definition formula - Q = i2rt (Joule's law) derivation formula - Q = w = uit, q = (U2 / R) t the premise of these two derivations is that the circuit is a pure resistance circuit, that is, when the current passes through the conductor, all the electric energy is converted into internal energy, but not into other forms of energy at the same time, that is, all the work done by the current is used to generate heat
(4) The heater of electric heater has high resistivity and high melting point. Fuse is lead antimony alloy wire with high resistivity and low melting point
(5) Electric heating features:
a. Electrothermal characteristics: whether it is a series circuit or a parallel circuit, the total heat generated in the circuit is equal to the sum of the heat generated by all electrical appliances, that is, qtotal = Q1 + Q2
b. The relationship between electric heating and resistance in series circuit: the electric heating produced by various electrical appliances (resistance) in series circuit is directly proportional to its resistance, that is, Q1 / Q2 = R1 / R2
c. The relationship between electric heat and resistance in parallel circuit: the electric heat produced by various electrical appliances (resistance) in parallel circuit is inversely proportional to its resistance, that is, Q1 / Q2 = R2 / R1
（3） For the connection mode of two basic circuits, it is required to master the drawing method of typical circuit diagram, connection of physical circuit diagram, current characteristics, voltage characteristics, equivalent resistance, electric power characteristics, electric power characteristics and electrothermal characteristics
（4） For an important electrical experiment -- voltammetry, we should master the conventional processing methods in the specific experiment of measuring resistance and electric power, including its experimental instruments, experimental principles, circuit diagrams, operation methods, etc
Drawing method of typical circuit diagram, connection of physical circuit diagram, current characteristics, voltage characteristics, equivalent resistance, electric power characteristics, electric power characteristics and electrothermal characteristics
Typical circuit drawing method: left input, right output. Upper positive and lower negative
Who has asked for all the formulas about electric power, resistance, electric work, current, voltage and heat?
Current I a (a) a i = u / R
Voltage U V U = IR
Resistance R ohm (Ω) r = u / I
Electric work w Joule (joule) J W = uit
Electric power P watt (watt) W P = w / T = UI
Heat Q Joule J Q = cm (T-T °)
Given the electric work and power, how to calculate the current, voltage and resistance?
Given the electric work Q and electric power P, how to calculate the current I, voltage U and resistance R needs to use the following formula:
From P = I ^ 1 * r, r = P / I ^ 2 or I = √ (P / R) can be derived
From P = u ^ 2 / * r, r = u ^ 2 / P or u = √ (p * r) can be derived
From q = P * t, P can be obtained when the time t is known, and then u, I, R and other parameters can be obtained through the above formula
A light bulb marked with 36V 9W is now connected to the home circuit (voltage is 220V) for use
In order to make the small bulb shine normally, what is the resistance in series?
Bulb resistance RL = u & # 178 / P = 36 & # 178 / 9 = 144 Ω
Required series resistance R = (220-36) △ 36 × 144 = 736 Ω
Because it is connected in series, the current is equal. When the small bulb is normally emitting, the current is I = P / u = 9W / 36V = 0.25A, so the resistance current is also 0.25A, and the voltage at both ends of the resistance is 220v-36v = 184v, so the resistance R = u / I = 184v / 0.25A = 736 Ω
What is the condition for the load to get the maximum power from the power supply
The condition that the load obtains the maximum power from the power supply is that the load impedance is the same as the internal impedance of the power supply
Assuming that the source potential is e, the internal impedance is r, and the load impedance is r, the power obtained by the load p = [E / (R + R)] ^ 2XR = e ^ 2 x R / (R + R) ^ 2, it can be deduced that when r = R, P can obtain the maximum value, and the maximum power is p = e ^ 2 / (4R)
Why is the increase of temperature, the increase of metal resistivity and the decrease of semiconductors and insulators
I want to understand that the resistivity of the material depends on its microstructure and temperature
Because metals conduct electricity by the movement of electrons, when the temperature rises, the nucleus moves faster, which hinders the directional movement of electrons and increases the resistance. Semiconductors conduct electricity by crystal defects. When the temperature rises, the vacancy moves faster, so the resistance is small There is no absolute insulator
The voltage of the home circuit is 220 V, and a lamp with a resistance of 1100 Ω. When it works normally, how many amperes does the current pass through it? (it needs a process, and each data needs a unit)
Is the rated voltage of your bulb 220 V
I=U/R=220V/1100Ω=0.2A
It is known that the electromotive force E of the DC circuit is 120V. When the circuit is working, the voltage of the power supply terminal is 110V and the current of the circuit is 2
The power supply voltage is equivalent to the circuit voltage when the circuit is working
Then the external resistance of the whole circuit is 55 ohm
The internal resistance is 10 ohm
I don't know what else you don't understand
What are you asking? Be more specific.
The voltage of power supply terminal is equivalent to the voltage of external circuit when the circuit is working
Then the external resistance of the whole circuit is 110V / 2A = 55 Ω
The internal resistance is (120v-110v) / 2A = 5 Ω
What's the problem?
What do you want
The resistivity of semiconductors decreases with the increase of temperature. Will some semiconductors become superconductors when the temperature rises to a certain extent
It is impossible. According to the change formula of resistivity with respect to temperature coefficient, and according to the experimental results, there is a certain limit for this reduction. Beyond the limit, it cannot be reduced
Yes, glass can become a conductor when the temperature rises``
It's not rising, it's falling to a certain temperature. Now high temperature superconductivity is the world