قانون اوم - المحرض والتحريضية - قوانين الدارة ووحدات قياسها .. الإلكترونيات

Ohm's Law - Inductor and Inductance -
Circuit Laws and Units of Measurement .. Electronics

Circuit Laws and Units of Measurement

If the voltage applied to an electrical circuit increases, the intensity of the current passing through it increases (21), and if its value decreases, the intensity of the current passing through the circuit weakens. However, if the value of the applied voltage remains constant, and the resistance increases, the intensity of the current passing through the circuit decreases (22). As for decreasing the resistance of the circuit, it will increase the intensity of the current passing through it. These facts are the foundations on which Ohm's Law was built, which states the following:

Current in amperes × resistance in ohms Voltage - in volts

Or in short, T x M = C, where T represents the intensity of the current, M the resistance, and C the voltage.

This equation can be written as follows:
C / T = M, or, C / M = C.

It must always be remembered that the basic units of an electrical circuit are the ampere, volt, and ohm. Example: Calculate the voltage drop that occurs when a current of 1 milliamp passes through a 100 kΩ resistor.

The solution is:

G = T × M = 0.001 × 000 100 = 100 volts.

As for the power utilized or the power lost or missing in the circuit, it is measured in watts. Examples of utilized power include those used to raise the temperature of heating wicks in valves or to operate a loudspeaker or any other device.

21 - Increase in current due to increased voltage.
22 - Decrease in current due to increased resistance.
Current = Voltage / Resistance

23 - Electrical power of the circuit (power in watts - voltage × current).
24- Voltage - Resistance - Current - Power.

Examples of lost power include those lost in heating a resistor used to reduce the voltage of the circuit, and we can calculate the power utilized in the output of the amplifier or any device in watts. Small capacities are calculated in milliwatts (1000 milliwatts = 1 watt).

The equation is:
Power in watts = voltage × current
Watts / volts = amperes, or also, Watts / amperes = volts

It is known that a car lamp with a capacity of 36 watts and powered by a 12-volt battery (23) draws a current of 36/12 = 3 amperes, and if a voltage of 10 volts is applied across the ends of a resistor with a value of 400 ohms, the current passing through it will be (24 A).

V = V / m = 10/400 = 0.25 amperes.

If the same voltage is applied to two resistors in series, one of which is 8000 ohms and the other is 2000 ohms (24 b), the total resistance becomes 8000 + 2000 = 10000 ohms.

The current passing through them is
V = V / M = 100 / 10000 = 0.21 amperes = 10 milliamps

Inductor and inductance

The inductor is a wire coil, when the current begins to pass through it, a magnetic field is created in it that tries to obstruct the flow of the current, and when the current is cut off or changes direction, this field collapses, generating an electromotive force (E.D.K.) that tries to keep the current flowing in the same previous direction, i.e. it tries to prevent changes that occur to the current. Figure 125 shows an inductor 1 connected to a source and to a source of alternating current, i.e. a source of current whose direction changes rapidly. Figure (25b) shows another inductor that contains a larger number of turns and thus opposes the passage of current with a greater force than the first. The inductor that contains a larger number of coils is characterized by a greater inductance than the others, and the extent to which the inductive coils provide resistance to the passage of current in an amount in ohms is usually called "reactance".

Figure (126) shows a circuit that includes an alternating current source with a frequency of 50 Hz or 50 cycles per second, meaning that its direction changes from positive to negative 50 times every second. As for Figure (26b), the frequency is 100 cycles per second, and in it we find that the value of the reactance in ohms for the same inductance has doubled compared to the first case, and this is due to the increase in reactance with the increase in frequency.

The "henry" is the unit of measurement of inductance. Its parts are "millihenry and microhenry".

25 - The coil reactance increases with the increase in Inductive.
26 - The coil reactance increases with increasing frequency.