Resistance in series and parallel
Parallel circuit
resistance in parallel shows three parallel circuit resistance connected in series. Obviously, the current flowing through each resistance will be the same but the voltage drop across each of them will vary as per the value of individual resistance.
Also, the sum of all the voltage drops V1+V2+V3 is equal to the applied voltage V
V= V1+V2+V3
IR= IR1+IR2+IR3
R= R1+R2+R3
Where R is the equivalent resistance of a series combination.
Also,
As seen above, the main characteristics of a series circuit are
- The same current flows through all parts of the circuit.
2. Different resistors have their individual voltage drops.
3. voltage drops are addictive.
4. Applied voltage equals the sum of different voltage drops.
5. Resistance is additive.
6. Powers are additive.
Voltage divider rule
Since in a series circuit, same the same current flows in each of the given resistors, voltage drops vary directly with its resistance shown in the figure below. A 45-volt battery is connected across a series combination of three resisters. resistance in parallel
Total resistance, R= R1 + R2+ R3= Ohm.
According to the voltage divider rule, various voltage drops are:
V1=V.R1/R
V2=V.R2/R
V3=V.R3/R
Resistance in parallel
resistance in parallel In this parallel circuit case voltage across each resistance will be the same but the current will be different depending upon the value of individual resistance. parallel circuit
I = I1+ I2+ I3
V/R =V/R1+V/R2+V/R3
1/R =1/R1+1/R2+1/R3
Where R is the equivalent resistance of the parallel combination.
R = R1R2R3/R1R2+R2R3+R3R1
The main characteristics of a parallel circuit are:
1. Same voltage acts across all parts of the circuit.
2. Different resister have their individual current.
3. Branch currents are additive.
4. Conductance is additive.
5. Powers are additive.
What is Resistor
A resistor entails the following two main characteristics:
1. Its resistance R in ohm. The resistors are available from a fraction of an ohm to many mega ohms.
2. The wattage rating. The power rating may be as high as several hundred watts or as low as 1/10 watts. Power rating indicates the maximum voltage the resistor can dissipate without excessive heat.
Classification of Resistor
The resistor is classified as follows
1. Fixed resistor. The fixed resistor is the simplest type of resistor fixed means that the unit is so constructed that its resistance value is constant and unchangeable. These are made of a carbon composition and have a cover of black or brown hard plastic.
2. Tapped resistor. A tap resistor is a resistor that has a tap, or connection, somewhere along the resistance material. These resistors are usually wire wound type. If they have more than one tap, they will have a separate terminal for each.
3. Variable resistor. A variable resistor has a movable contact that is used to adjust or select the resistance value between two or more terminals. A variable resistor is commonly called a control.
4. Special resistor. the most common type of special resistor is the fusible type. A fusible resistor has a definite resistance value and it protects the circuit much like a fuse. Another special resistor is the temperature-compensating unit. Such resistors are used to provide special control of circuits that must be extremely stable in their operation.
