Is impedance and resistance the same?

Is impedance and resistance the same?

impedance
Impedance
In a circuit with resistance, inductance and capacitance, the blocking effect on alternating current is called impedance. Impedance is usually represented by Z. impedance consists of resistance, inductive reactance and capacitive reactance, but it is not a simple sum of them. The unit of impedance is Ohm. In direct current, the blocking effect of objects on current is called resistance. All substances in the world have resistance, In the field of alternating current, however, in addition to the fact that the resistance will hinder the current, the material with small resistance is called good conductor, such as metal, and the material with great resistance is called insulator, such as wood and plastic, The reactance of capacitance and inductance are called capacitive reactance and inductive reactance respectively. Their unit of measurement is Ohm like resistance, and their value is related to the frequency of alternating current. The higher the frequency, the smaller the capacitive reactance and the greater the inductive reactance, The lower the frequency is, the larger the capacitive reactance is and the smaller the inductive reactance is. In addition, the capacitive reactance and the inductive reactance also have the problem of phase angle, which has the relationship of vector. Therefore, it can be said that impedance is the sum of resistance and reactance in vector. For a specific circuit, impedance is not constant, but changes with the change of frequency, Generally speaking, the impedance of a circuit is larger than that of a resistance. That is to say, the impedance decreases to the minimum. In a parallel circuit of inductance and capacitance, the impedance increases to the maximum at resonance, which is opposite to that of a series circuit
resistance
Definition: the resistance of a conductor to current is called the resistance of the conductor
Resistor is the most commonly used component in all electronic circuits. The main physical feature of resistor is to change electric energy into heat energy. It can also be said that it is an energy consuming component. The current through it generates internal energy. Resistor usually acts as a voltage divider in the circuit. For signals, both AC and DC signals can pass through resistor
The unit of resistance is Ohm, which is indicated by the symbol "Ω". Ohm is defined as: when a voltage of 1 volt is applied at both ends of a resistor, if a current of 1 ampere passes through the resistor, the resistance of the resistor is 1 ohm, The unit of resistance is also kiloohm (K Ω), megaohm (m Ω), etc
The electrical performance index of resistor usually includes nominal resistance, error and rated power
It forms some functional circuits with other components, such as RC circuit
Resistance is a linear element. It is said that it is a linear element because it is found through experiments that under certain conditions, the current flowing through a resistance is proportional to the voltage at both ends of the resistance - that is, it conforms to Ohm's Law: I = u / R
The common carbon film resistor or metal film resistor can be simulated by linear resistor when the temperature is constant and the voltage and current values are limited within the rated conditions. If the voltage or current value exceeds the specified value, the resistor will not comply with Ohm's law due to overheating, or even be destroyed. The relationship between the working voltage and current of linear resistor is shown in Figure 1. There are many kinds of resistors, Usually divided into carbon film resistance, metal resistance, wire wound resistance, etc.: it also includes fixed resistance and variable resistance, photosensitive resistance, varistor, thermistor, etc
The unit of resistance is expressed in ohm. It includes? Ω (Ohm), K Ω (kiloohm) and m Ω (megohm)
1MΩ=1000KΩ ,1KΩ=1000Ω.
The method of marking resistance value is usually colored ring method and digital method. The color ring method is more common in general resistance. Because the resistance in mobile phone circuit is generally small, it is rarely marked with resistance value. Even if there is, the digital method is generally used, that is:
101 -- Resistance of 100 Ω; 102 -- Resistance of 1K Ω; 103 -- Resistance of 10K Ω; 104 -- Resistance of 100k Ω; 105 -- Resistance of 1m Ω; 106 -- Resistance of 10m Ω
If a resistor is 223, the resistor is 22K Ω. The general appearance of the resistor on the mobile phone board is shown in Figure 5. Its two ends are silver white, and most of the middle is black
Generally speaking, it is easy to judge the resistance by using a multimeter: adjust the multimeter to the right position of the resistance block, and put the two probes of the multimeter on both ends of the resistance, then the resistance value can be read out from the multimeter. It should be noted that the hand cannot touch the metal part of the probe when testing the resistance, In addition to a few types of resistance, but also rarely care about the resistance value. Pay attention to whether the resistance of false welding, desoldering

If the minimum value of quadratic function y = x2 + 4x + A is a, then the value of a is?
The minimum value of a should be 4.

Y = x2 + 4x + A is a quadratic function
Δ = b2-4ac ≤ 0, then 16-4a ≤ 0, then a ≥ 4

If we know that the perimeter of a square is x and the radius of its circumscribed circle is y, then the analytic expression of the function of Y with respect to X is ()
A. y=12x（x＞0）B. y=24x（x＞0）C. y=28x（x＞0）D. y=216x（x＞0）

As shown in the figure: ∵ the perimeter is x, X ＞ 0. ∵ BC = DC = x4, ∵ C = 90 °, ∵ BD is the diameter, ∵ BD is the hypotenuse of isosceles right triangle, ∵ BD = 2 · BC = 24x, that is, 2Y = 24x, ∵ y = 28x, X ＞ 0, so C is selected

The angle between the two diagonals of the rectangle is 120, the longer side is 3cm, the shorter side is 3cm

Analysis "you first draw a square ABCD (named from top to bottom, from left to right) suppose that the intersection of two diagonals is point O, and then make a vertical line on the right side (side BC) through point O, and the intersection side BC is point E. according to the known conditions you said, we know that the angle AOB is 120 degrees, then the angle BOC = 180 degrees - the angle AOB = 60 degrees; so the triangle BOC

The known set a = {x | x ^ 2 > = 0}, B = {x | x ^ 2-4x + 3

A = R, so AUB = R

Solving the equation 2x-1 = 5x-3

5x-2x=3-1
3x=2
x=2÷3
x=2/3

If f (x + 1) = 2x & # 178; - 4x, then what is the analytic expression of F (x)

Let t = x + 1
f(t)=2(t-1)²-4(t-1)
=2t²-8t+6
∴f(x)=2x²-8x+6

The computer uses binary, it has two numbers, 0, 1, to convert a decimal number into a binary number, as long as the number is written as the sum of several n square numbers of 2, write 1 or 0 in turn. For example, 19 (+) = 4 square of 1 * 2 + 3 square of 0 * 2 + 2 square of 0 * 2 + 1 square of 1 * 2 + 0 square of 1 * 2 = 10011 (=) (1) try to write 48 as a binary number. (2) if a binary number is 1001011, So what's the decimal number?

(1)48=2^5+2^4=110000
(2)1001011=2^6+2^3+2^1+1=75

If 1 / A + 1 / b = 4, then a-3ab + B / 2A + 2b-7ab =?
A question about Chifeng in 2007

a-3ab+b/2a+2b-7ab
Numerator and denominator divided by ab
=(a/ab-3ab/ab+b/ab)/(2a/ab+2b/ab-7ab/ab)
=(1/b-3+1/a)+(2/b+2/a-7)
=[(1/a+1/b)-3]/[2(1/a+1/b)-7]
=(4-3)/(8-7)
=1

What is the condition that the function y = f (x) has a limit at the point x0 that it has a definition in a neighborhood of the point (except the point)?
A is necessary, B is sufficient, C is sufficient, and D is irrelevant

If the function y = f (x) has a limit at the point x0, then it has a definition in a neighborhood of the point (except the point), which can be obtained from the definition of the limit
The simplest example is Dirichlet function
So it's a sufficient condition