电工电子技术基础与技能知识点汇总

电工电子技术基础与技能知识点汇总

XXX

1.Circuit: A closed loop consisting of a power source。electrical appliances。wires。XXX: XXX.

2.Circuit status: On (closed circuit)。off (open circuit)。short circuit。Short circuits can cause high currents that can damage the power source and wires。so they should be avoided.

3.Current: The movement of XXX must be met for current to flow: (1) There must be free charges。(2) XXX (potential difference) XXX.

4.The magnitude of current is equal to the。of the amount of XXX's n to the time it takes to pass.

I = q/t

5.Ohm's law: XXX its length。XXX its nal area。and dependent on the material properties of the conductor。while the temperature remains constant.

R = ρl/S

6.In general。the XXX by temperature and are used to make standard resistors。Superconductivity: XXX (near absolute zero)。XXX.

7.Electrical energy: The work done by the electric field force

is the electrical XXX circuit。The actual process is the XXX energy into other forms of energy。1 degree U = 1 kW·h = It·3.6

× 106 J.

8.Power: The。of the XXX.

P = W/t or P = UI

9.JouleXXX to the square of the current。the resistance of the conductor。and the n of the current.

Q = I2Rt

10.Electromotive force (EMF) of a power source: The voltage een the two poles of a power source when it is not connected to a circuit。It is XXX(1) The EMF is determined by the power source itself and is independent of the external circuit。(2) The n of the EMF is from the negative pole through the power source to the positive pole.

11.The EMF is independent of the external circuit resistance。but the voltage at the power source terminal changes with the load。As the external resistance increases。the terminal voltage increases。and as the external resistance decreases。the terminal voltage decreases。When the external circuit is open。R tends to infinity。I。U。E。R。and I are related by Ohm's law。When

the external circuit is shorted。R tends to zero。I tends to infinity。and U tends to zero.

12.When R = R0.the power output of the power source is maximum。but the efficiency of the power source is only 50%。This is called matching the load to the power source.

Pmax = E2/4R

13.In a series circuit。the current is the same everywhere。the total voltage of the circuit is equal to the sum of the voltages across each part of the circuit。the total resistance is equal to the sum of the resistances。and the XXX its resistance.

14.XXX with a full-scale current of Ig and internal resistance of Rg into a voltmeter with a range of U。the nal resistor R is:

R = (U - IgRg)/Ig

在并联电路中，每个支路的电流是独立的，可以通过支路电流法来求解电路中的各个参数。根据这个法则，各支路两端的电压相等，电路中总电流等于各支路电流之和，总电阻的倒