# Determining resistors in AC/DC circuit

• johnsholto
In summary, the circuits described involve a black box connected to an AC/DC circuit where the values of U and I are given in the DC circuit and the value of R is not, while the values of U and R are given in the AC circuit and the value of I is not. The resistor used is a variable resistor, which is used to control the current flow and adjust resistance in a circuit.
johnsholto
I have trouble with determining the type of resistor used in the following problem.

A type of black box is connected to an AC/DC circuit. The values of U and I are given in the DC circuit, the value of R is not. The values of U and R are given in the AC circuit, the value of I is not.

In the DC circuit the values of U and I are.
U=0 I=0
U=1 I=360
U=2 I=500
U=3 I=650
U=4 I=750
U=5 I=850

Now, R is calculated using U=R*I, right?

So the values of R would be:
R0=-
R1=1/360
R2=1/250
R3=3/650
R4=2/375
R5=1/170

In the AC circuit the values of U and R are:
U=0 R=0
U=1 R=2.7
U=2 R=3.3
U=3 R=4.5
U=4 R=5.3
U=5 R=5.8

The values for I would be according to U=R*I:
I0=-
I1=0.37
I2=0.6
I3=0.66
I4=0.75
I5=0.86

Now, how do I determine the type of resistor that has been used in these circuits? I assume that it is not a capacitor as there is current flow in the DC circuit.
Furthermore, the values of I in the AC circuit is approximately the value of I in the DC circuit*1/1000.

Based on the values of U and R in the AC circuit, it can be seen that the resistor used is a variable resistor. Variable resistors are typically used to control the current flow in a circuit and adjust its resistance as needed.

## 1. What is the purpose of determining resistors in an AC/DC circuit?

The purpose of determining resistors in an AC/DC circuit is to calculate the amount of resistance present in the circuit. This helps in understanding the behavior of the circuit and how it affects the flow of electricity.

## 2. How do you calculate the total resistance in an AC/DC circuit?

The total resistance in an AC/DC circuit is calculated by summing up the individual resistances present in the circuit. This includes both series and parallel resistors. For series resistors, the total resistance is equal to the sum of all the individual resistances. For parallel resistors, the total resistance is calculated using the formula 1/Rt = 1/R1 + 1/R2 + 1/R3 ... where Rt is the total resistance and R1, R2, R3, etc. are the individual resistances.

## 3. How does the frequency of the AC current affect the resistance in a circuit?

The frequency of the AC current does not directly affect the resistance in a circuit. However, it does affect the behavior of certain types of resistors, such as capacitors and inductors, which have a frequency-dependent resistance known as reactance. This means that the resistance of these components will change with the frequency of the AC current.

## 4. Can you use the same formula to calculate resistance in both AC and DC circuits?

Yes, the formula for calculating resistance (R = V/I) can be used for both AC and DC circuits. However, in AC circuits, the resistance may vary due to the frequency-dependent reactance of certain components, as mentioned earlier.

## 5. How do you measure the resistance in an AC/DC circuit?

In order to measure the resistance in an AC/DC circuit, you can use a multimeter. Set the multimeter to the resistance (ohms) setting and connect the probes to the points in the circuit where you want to measure the resistance. The multimeter will display the resistance reading in ohms. Alternatively, you can use the formula R = V/I and measure the voltage and current in the circuit using a voltmeter and ammeter, respectively.

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