Factors affecting electrical resistance

• Length of the wire
• Cross-sectional area of ​​the wire
• temperature
• Material type

In order to know the effect of various factors on electrical resistance, we must first learn about Ohm’s law, which states that the electrical potential difference between the two ends of a metal conductor is directly proportional to the intensity of the electrical current passing through it, and a lot of information can be obtained through this law, To calculate the electrical voltage, we use this relationship: (V=I*R), to calculate the value of the electric current: (I=V/R), and to calculate the value of electrical resistance: (R=V/I).

We will conduct an experiment on two stations in an electric current to extract the relationship between the factors affecting electrical resistance and current intensity:

Wire length:  We imagine that there is a copper wire 1 m long, connecting point A and B in the electrical circuit. We record the value of the electric current, then we take another copper wire with the same cross-sectional area but different in length. The length of this wire is about 2 m. By connecting the two ends through the new copper wire, we remove the old wire, then we record the value of the new wire, and we discover that the electric current in the second case is half the value of the electric current in the first case, and to explain the situation mathematically, we use Ohm’s law.

• Since the value of the electric current I = V / R, the electrical resistance in the second case increased twice as much as the first case
• This means that the resistance is directly proportional to the length of the wire.
• Therefore, increasing the length of the wire means increasing the electrical resistance and decreasing the value of the electric current

Cross-sectional area of ​​the wire:  In the second case, take two copper wires of the same length with different cross-sectional area, make the cross-sectional area of ​​the first wire greater than the cross-sectional area of ​​the second wire, connect the first wire between points A and B in the electrical circuit, and record the intensity of the electric current. Now disconnect the first wire, connect the second wire between the electrical current terminals, and read the ammeter again. You will notice that the electrical current is higher in the first wire than the electrical current in the second wire, which had a smaller cross-sectional area.

• Resistance to electric current is inversely proportional to the cross-sectional area of ​​the wire
• The resistance of a wire with a small area, i.e. a thin wire, is greater than the resistance of a thick wire.

Type of material:  Resistance in an electrical circuit is related to the type of material. If we take a copper wire and an aluminum wire, and connect each of them separately, we will notice a difference in electrical resistance. Connect the copper wire between terminals A and B and record the value of the electrical current, then disconnect the copper wire. Place the aluminum wire between terminals A and B, and record the value of the electric current. You will notice that the value of the electric current in the copper wire is higher than the value of the electric current in the aluminum wire.

• This means that the resistance of the copper wire is less than that of the aluminum wire
• The resistance of the wire depends on its quality

Effect of temperature: If the temperature associated with the electrical circuit increases, the resistance will increase, and therefore temperature is considered one of the factors that affect the value of electrical resistance.

Examples of resistance in an electrical circuit

Electrical resistance is an important element of the electrical circuit, and electrical resistance has many types

• Fixed resistors:  such as carbon and wire resistors. The wire resistance is fixed and does not change and is written in numbers or colors. As for the carbon resistance, the resistance is made of carbon, so its resistance is very large and the intensity of the current is low, unlike the wire resistance, which is small, because it is made of a wire wound on a wire. The body of the resistor, its value is qualitatively small while the current intensity is higher. Carbon resistors can be calculated either with a special device or by the colors of the resistor.
• Variable resistors: They are either mechanical, optical resistance, or thermal resistance. Mechanical resistance is installed by winding or sliding. Optical resistance is by converting light into resistance. The resistance decreases when the intensity of lighting increases, and the resistance increases as the intensity of light decreases. As for the thermal resistance, it is an electronic element. It converts heat into resistance whose value varies depending on the ambient temperature.

Ohm’s Law To calculate electrical voltage, we use this relationship: (V=I*R), to calculate the value of the electric current: (I=V/R), and to calculate the value of electrical resistance: (R=V/I).

That is, through Ohm’s law, we can deduce the value of electrical resistance, and we will present examples in order to further confirm the idea

Example 1: Find the resistance of the electric current if the value of the electric current is 0.3 A and the applied potential difference is 0.9 V.

• Electrical current 0.3 A
• The potential difference applied to the electrical current is 0.9 V.
• We apply the electrical relationship R = V / I, we substitute the values ​​= 0.9/0.3, so the electrical resistance equals = 3 Ω ohms

Second example: The heater has a resistance of 50 Ω and is connected to a 220 V source. Calculate the current in the heater.

• We have the following information: The resistance of the heater is 50 ohms
• The electric potential difference is 220 volts
• We substitute this information into Ohm’s law, which is V = I × R
• We rearrange the expression to obtain the calculation of electric current, which is I = V / R
• We substitute the numbers = 220/50
• = 4.4 A
• The electric current is 4.4 amps

What are the factors that affect the resistance value?

The electrons that pass through the electrical wires in the electrical circuit face resistance, and resistance, in its simple definition, is the resistance to the passage of current. The path of the electron from one point to another point is not a straight path, but rather a winding path that faces many types of obstacles, and these are the obstacles that the electron faces in order to reach it. From one point to another, it is the resistance, and the resistance can increase or decrease, and the resistance in the electrical circuit is related to several elements, which are:

• temperature
• Length of electrical cord
• Sectional area
• The nature of the wire

Temperature : Resistance increases with temperature. This means that the resistance of the wire increases with the temperature in the wire

Length of the electrical wire : Resistance is directly proportional to the length of the electrical wire, and as the length of the electrical wire increases, the electrical resistance increases

Cross-sectional area : Resistance increases as cross-sectional area decreases. This means that resistance is inversely proportional to the cross-sectional area of ​​the wire.

Nature of the material:  The nature of the material affects the resistance of the electrical wire

Combining these relationships and factors brings us to the relationship that electrical resistance is directly proportional to the length of the wire and inversely proportional to the cross-sectional area of ​​the wire, and this means that R=p*L/ِِA