Different definitions
Resistance is a parameter of a resistive element, obtained by dividing the voltage of the resistor by the current; Reactance is a parameter of inductance and capacitance, where the voltage of the inductance is divided by the current to obtain the inductance, and the voltage of the capacitance is divided by the current to obtain the capacitance. Inductance and capacitance are collectively referred to as reactance.
Different physical meanings
Resistance is generated by the resistive properties of a conductor. When current passes through a conductor, it generates the motion of electrons and the interaction with atoms, resulting in resistance.
Impedance is generated by the comprehensive influence of components such as resistance, inductance, and capacitance. When AC current passes through a circuit, electromagnetic induction is generated, resulting in the influence of inductance and capacitance.
Current difference
Resistance exists in both DC and AC circuits, while reactance only exists in AC circuits. The size of resistance is independent of voltage and current, and does not change with changes in voltage and current; The magnitude of reactance varies with the frequency of voltage and current, with inductive reactance proportional to frequency and capacitive reactance inversely proportional to frequency.
Different properties
Impedance: In a circuit with resistance, inductance, and capacitance, the resistance to the current in the circuit is called impedance.
Resistance: A resistor is a current limiting element that, when connected to a circuit, has a fixed resistance value, usually two pins, which can limit the amount of current passing through the branch it is connected to.
Different influencing factors
Impedance: The ratio of the peak voltage (or effective value) Um at both ends of a passive circuit in an AC circuit to the peak current (or effective value) Im passing through the circuit is called impedance, expressed in z and expressed in ohms (Ω). When U is constant, the larger z, the smaller I, and the impedance has a limiting effect on the current.
Resistance: The resistance value of a resistive component is generally related to temperature, material, length, and cross-sectional area. The physical quantity that measures the influence of temperature on resistance is the temperature coefficient, which is defined as the percentage of change in resistance value for every 1 ℃ increase in temperature.
Different functions
Impedance: In audio equipment, impedance is often mentioned as an important parameter. For example, the impedance of amplifiers and speakers is often designed to be 8 ohms, because at this impedance value, the machine has the best working state. In fact, the impedance of a horn varies with the frequency, and the horn specifications usually indicate a rough average. Most products on the market are four ohms, six ohms, or eight ohms.
Resistance: If the resistance value of a resistor is close to zero ohms (such as a large cross-sectional wire between two points), the resistor has no obstruction to current, and the circuit connected in parallel with this resistor is short-circuited, resulting in an infinite current. If a resistor has infinite or large resistance, the circuit connected in series with the resistor can be considered as an open circuit with zero current.
Different applications
Resistors are commonly used in DC circuits to limit the magnitude of current and regulate the power of the circuit.
Impedance is commonly used in AC circuits to describe the effect of components on AC current in the circuit