Gurumuda Networks
If the spring is connected in series, as in the figure on the side, then:
1. The increase in the length of spring = the increase in length 1 + the increase in length 2
Δy = Δy1 + Δy1
2. The force experienced by equivalent spring = the force experienced by spring 1 = the force experienced by spring 2
Fs = F1 = F2
If the spring is pulled to the right, the spring will stretch and increase in length (figure 1). If the pull force is not huge, it is found that the increase in spring length (Δx) is proportional to the magnitude of the pull force (F). In other words, the greater the pull force, the greater the length of the spring. Comparison of the magnitude of the pull force (F) and the increase in the spring length (Δx) is constant.
In almost all metal conductors, the electric field is proportional to the density of the electric current, where the ratio of the electric field to the electric current density is constant. Mathematically expressed through the equation:
ρ = E / J
E = electric field, ρ = resistivity, J = current density
The constant ρ is called resistivity, whose value is constant and does not depend on the electric field that gives rise to the electric current.
Regarding electric current, the density of electric current has been discussed, so also the electric field has been explained in-topic about the electric field. The electric field and electric current are in a conductor if there is a potential difference in the conductor, whereas if there is no potential difference, then there is also no electric field and electric current.
In almost all metal conductors, the electric field is directly proportional to the density of the electric current, where the ratio of the electric field to the density of the electric current is constant. The value of the comparison of the electric field to current density is called resistivity. Mathematically, the relationship between the electric field, current density, and resistivity is stated in the equation:
The resistor is one component of an electrical circuit that functions to control the number of electric currents. In general, there are two types of resistors, namely wire coil resistors and carbon resistors. Wire roll resistors are usually used in the laboratory, made by wrapping fine wire on the surface of the insulator tube. Carbon resistors are typically used in electronic circuits, cylindrical, and have wires at both ends. The value of the carbon resistor resistance is expressed in color code and displayed on the surface of the resistor.
The resistance value of a resistor can be known by interpreting the resistor color code. To understand this, first look at the following table, then study the example problem to determine the resistor resistance value.
If the resistors are connected as shown in the figure, the resistors are arranged in series. Resistor or electrical resistance in question can be in the form of resistor components, lights, or other electrical resistance.
The electric charge moves through resistance 1 (R1) = the electric charge moves through resistance 2 (R2) = the electric charge moves through resistance 3 (R3). Electric current (I) is an electric charge that flows during a certain time interval (I = Q / t), hence the electric current through resistance 1 (I1) = electric current through resistance 2 (I2) = electric current through resistance 3 (I3). Mathematically, the total electric current (I) = I1 = I2 = I3.
In the topic of Ohm’s law, a formula that states the relationship between the voltage (V), electric current (I), and electrical resistance (R) has been derived. Mathematically expressed through equations:
This equation shows that the electrical resistance (R) is directly proportional to the electric voltage (V) and inversely proportional to the electric current (I). If the mains voltage is greater than the electrical resistance is getting bigger, on the contrary, if the stronger the electric current gets bigger than the electrical resistance will be greater. This equation explains Ohm’s law only when the electrical resistance (R) is constant. If the electrical resistance is not constant, then this equation does not explain Ohm’s law, but explains the resistance of a conductor.
If the resistors are connected as in the figure, the resistors are connected in parallel.
The electric current (electric current = electric charge that flows during a time interval) that enters the junction point is the same as the electric current exit from the junction point. There are several junctions so that the total electric current = the amount of electric current flowing in each junction. Mathematically, I = I1 + I2 + I3. While the electric potential difference or electrical voltage in each junction is the same.
I = V/R so the above equation changes to I = V/R1 + V/R2 + V/R3. The electric voltage is equal, so this equation changes to I = V (1/R1 + 1/R2 + 1/R3). If the equivalent resistance is 1/R then I = V (1/R). Thus, 1/R = 1/R1 + 1/R2 + 1/R3.
Electric current flows in a closed circuit, from high potential to low potential. When an electric current moves through a component of electrical resistance, there is a reduction in electrical potential energy because electrical energy is used on this resistance. In order for the electric current to continue to flow from high potential to low potential,
there must be a device to add electrical potential energy, the tool is an electromotive force (emf) or more accurately called an electric voltage source. Emf or a voltage source is a component that converts a type of energy into electrical energy, such as batteries, solar cells, or electricity generators.
EMFs in series and parallel
If there are two or more sources of electromotive (emf) connected as shown in the figure, the emf is arranged in series.
The equivalent voltage source (ε) is:
ε = ε1 + ε2 + εn
The equivalent internal resistance (r) is:
r = r1 + r2 + rn
The electric current flowing through the external resistance (R) is:
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