Definitions of Common Electrical Terms

This article summarizes and annotates some commonly used electrical engineering terms:
1. Resistivity---also called resistivity or specific resistance. It is a physical quantity that measures the conductivity of a material. It is represented by the letter ρ and its unit is ohm*mm2/m. It is numerically equal to the resistance value of a wire made of that material with a length of 1 meter and a cross-sectional area of ​​1 square millimeter at a temperature of 20C. The greater the resistivity, the lower the conductivity. The resistivity of a material changes with temperature. Its value is equal to the ratio of the increase in resistivity to the original resistivity when the temperature rises by 1C. It is usually represented by the letter α and its unit is 1/C.

2. Temperature coefficient of resistance---a physical quantity that indicates that the resistivity of a material changes with temperature. Its value is equal to the ratio of the increase in resistivity to the original resistivity when the temperature rises by 1C. It is usually represented by the letter α and its unit is 1/C.

3. Conductivity---the ability of an object to conduct current is called conductivity. In a DC circuit, the value of conductivity is the reciprocal of the resistance value. It is represented by the letter ɡ and its unit is ohm.

4. Conductivity - also known as conductivity coefficient, is also a physical quantity that measures the conductivity of a material. Its value is the reciprocal of resistivity, represented by the letter γ, and its unit is meter/ohm*mm square.

5. Electromotive force - the potential difference caused by the conversion of other forms of energy into electrical energy in a circuit is called electromotive force or simply electromotive force. It is represented by the letter E, and its unit is volt.

6. Self-inductance - when the current in a closed loop changes, the magnetic flux generated by the current passing through the loop itself also changes, so an induced electromotive force will also be induced in the loop. This phenomenon is called self-inductance, and this induced electromotive force is called self-induced electromotive force.

7. Mutual inductance - if there are two coils close to each other, part of the magnetic flux generated by the current in the first coil is linked with the second coil. When the current in the first coil changes, the magnetic flux linked with the second coil also changes, generating an induced electromotive force in the second coil. This phenomenon is called mutual inductance.

8. Inductance - a general term for self-inductance and mutual inductance.

9. Inductive reactance----When AC current passes through a circuit with inductance, the inductance has the effect of hindering the AC current from passing through. This effect is called inductive reactance, which is represented by Lx, Lx=2πfL.

10. Capacitive reactance----When AC current passes through a circuit with capacitance, the capacitance has the effect of hindering the AC current from passing through. This effect is called capacitive reactance, which is represented by Cx, Cx=1/12πfc.

11. Pulsating current----The current whose magnitude changes with time but whose direction remains unchanged is called pulsating current.

12. Amplitude----The maximum value of alternating current in a cycle is called amplitude.

13. Average value----The average value of alternating current refers to the ratio of the total charge flowing through the circuit in a certain period of time to the time period. The average value of a sinusoidal quantity usually refers to the average value in the positive half cycle, and its relationship with the amplitude value is: average value=0.637*amplitude value.

14. Effective value----In two identical resistors, direct current and alternating current pass through them respectively. If the heat they emit is equal after the same time, then the magnitude of this direct current is taken as the effective value of this alternating current. The effective value of a sinusoidal current is equal to 0.707 times its maximum value.

15. Active power - also called average power. The instantaneous power of alternating current is not a constant value. The average value of power in a cycle is called active power. It refers to the power consumed by the resistance part of the circuit, represented by the letter P, and the unit is watt.

16. Apparent power - in a circuit with resistance and reactance, the product of voltage and current is called apparent power, represented by the letter Ps, and the unit is watt.

17. Reactive power - in a circuit with inductance and capacitance, these energy storage elements convert the power supply energy into magnetic field (or electric field) energy in half a cycle and store it, and return the stored magnetic field (or electric field) energy to the power supply in the other half of the cycle. They only exchange energy with the power supply and do not actually consume energy. We call the amplitude value of the rate of energy exchange with the power supply reactive power. It is represented by the letter Q, and the unit is Zhi.

18. Power factor - in a DC circuit, voltage multiplied by current is active power. But in an AC circuit, voltage multiplied by current is apparent power, and the part of power that can do work (i.e., active power) will be less than the apparent power. The ratio of active power to apparent power is called power factor, represented by COSφ.

19. Phase voltage----The voltage between the three-phase transmission line (live wire) and the neutral line is called phase voltage.

20. Line voltage----The voltage between the lines (live wires) of a three-phase transmission line is called line voltage, and the magnitude of the line voltage is 1.73 times the phase voltage.

21. Phasor----In electrical engineering, the vector used to represent the magnitude and phase of a sinusoidal quantity is called a phasor, also called a vector.

22. Magnetic flux----The product of magnetic induction intensity and the area perpendicular to the direction of the magnetic field is called magnetic flux, represented by the letter φ, and the unit is Maxwell.

23. Magnetic flux density----The magnitude of the magnetic flux passing through a unit area is called magnetic flux density, represented by the letter B, and the magnetic flux density and magnetic field induction intensity are equal in value.

24. Magnetic resistance - Similar in meaning to resistance, magnetic resistance is the resistance of a magnetic circuit to magnetic flux. It is represented by the symbol Rm and its unit is 1/henry.

25. Magnetic permeability - also known as the magnetic permeability coefficient, is a coefficient that measures the magnetic conductivity of a material. It is represented by the letter μ and its unit is henry/meter.

26. Hysteresis - During the repeated magnetization process of a ferromagnetic body, the change in its magnetic induction intensity always lags behind its magnetic field intensity. This phenomenon is called hysteresis.

27. Hysteresis loop - In a magnetic field, the relationship between the magnetic induction intensity and the magnetic field intensity of a ferromagnet can be represented by a curve. When the magnetizing magnetic field changes periodically, the relationship between the magnetic induction intensity and the magnetic field intensity in the ferromagnet is a closed line. This closed line is called a hysteresis loop as shown in Figure 1.

28. Basic magnetization curve: The shape of the hysteresis loop of a ferromagnet is related to the maximum value of the magnetic induction intensity (or magnetic field intensity). When drawing the hysteresis loop, if different values ​​are taken for the maximum value of the magnetic induction intensity (or magnetic field intensity), a series of hysteresis loops will be obtained. The curve connecting the vertices of these loops is called the basic magnetization curve.

29. Hysteresis loss: A ferromagnet placed in an alternating magnetic field will produce some power loss due to the hysteresis phenomenon, which will cause the ferromagnet to heat up. This loss is called hysteresis loss.

30. Breakdown: The phenomenon of violent discharge or conduction of insulating materials under the action of an electric field is called breakdown.

31. Dielectric constant: Also called dielectric constant, dielectric coefficient or permittivity, it is a coefficient that represents the insulation capacity characteristics, represented by the letter ε, and the unit is farad/meter.

32. Electromagnetic induction: When the magnetic flux that links a conductor changes, an electromotive force appears in the conductor. This phenomenon is called electromagnetic induction.

33. Skin effect---also called skin effect. When high-frequency current passes through a conductor, the current will be concentrated on the surface of the conductor. This phenomenon is called skin effect.