The DC resistance and AC resistance of tungsten wire are indeed different, mainly reflected in the following aspects:
- Definition and characteristics
DC resistance:
DC resistance refers to the resistance to current in a DC circuit, which is the resistance presented by the component when DC is passed.
It is manifested as the inherent static resistance of the component, and the resistance value does not change with time. It is generally determined by the fixed resistance value of the electronic devices in the circuit.
DC resistance follows Ohm’s law, that is, resistance is equal to the ratio of voltage to current (R=V/I).
AC resistance:
In a circuit with resistance, inductance and capacitance, the resistance to AC is called impedance.
Impedance consists of real and imaginary parts, of which the real part is called resistance (R) and the imaginary part is called reactance, including capacitive reactance (Xc) and inductive reactance (XL).
The resistance of AC resistance changes with time, because the current constantly changes in the positive and negative directions, so it is commonly known as alternating resistance or impedance.
Its calculation requires the use of vector method, that is, Z=√[R²+(XL-Xc)²].
- Current flow direction and resistance change
DC resistance:
The current in DC resistance can only flow in one direction.
The resistance value of DC resistance does not change with time and is constant.
AC resistance:
The current in AC resistance will constantly change in the positive and negative directions.
The resistance value of AC resistance changes with time because it will be affected by components such as inductance and capacitance in the circuit.
- Power supply properties and frequency characteristics
DC resistance:
DC resistance usually requires a stable power supply to ensure that the current flows in one direction.
DC resistance is constant for DC current and is not affected by frequency.
AC resistance:
AC resistance requires a variable power supply to ensure that the current can flow periodically in both directions.
AC resistance changes with frequency because the inductance and capacitance in the circuit will change with the frequency.
- Impedance calculation and measurement
DC resistance:
The impedance of DC resistance can be directly calculated by Ohm’s law.
Conventional resistance measuring instruments such as multimeters can be used for measurement.
AC resistance:
The impedance calculation of AC resistance needs to consider complex parameters such as the inductance and capacitance of the resistance element, which is usually expressed in complex form.
A special AC bridge or test instrument is required for measurement, and the effect of frequency on the measurement result is considered.
- Application scope
DC resistance:
Mainly used in DC circuits, such as electronic equipment, power supply, batteries, etc.
AC resistance:
More commonly found in AC circuits, such as AC power supplies, transformers, motors, etc.
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