# RESISTANCE

The electrical resistance is a measure of opposition of flow current through an object. While a resistor is a component which is used to provide the resistance in a circuit.

## RESISTOR

A resistor is a passive electronic component having two-terminal that implements electrical resistance as a circuit element. Its SI unit is ohm (Ω).

In electronic circuits, resistors are used to adjust signal levels, reduce current flow, voltage drop, to divide voltages (voltage divider circuit), bias active elements, and terminate transmission lines etc.

When a resistor is used in series circuit, current flowing through each resistor is equal but the voltage present across each resistor is only part of the total circuit voltage.

### HOW DOES A RESISTOR WORK?

The resistor converts electrical energy into heat, which is then dissipated into the atmosphere. That’s why when a resistor is placed under a voltage it generates heat; don’t try to touch them in high voltage circuits but carefully can be checked by hands with 5V.

### WHAT IS THE MAIN FUNCTION OF A RESISTOR IN A CIRCUIT?

The main function of resistors in a circuit is to control the flow of current and dropping the voltage. For example; take an LED (light emitting diode) requires 2V and 10mA current, if 5V voltage & 100mA current flows through an LED will damage the LED. So a resistor is used to limit the current and dropping voltage.

Resistance depends on the resistivity of the material. The resistivity of the air is 1.3 × 10^16 to 3.3 × 10^16 Ω-m at 200° C. With no ions in the gas and/or in water its resistance is infinity. So, the resistance of any gaseous material or water depends on the ion content of that.

## HOW TO FIND RESISTANCE OF RESISTOR

### FIND RESISTANCE USING MULTIMETER

Rotate the multimeter knob over resistance, as the resistor has no polarity connect red wire to one terminal and black to another, this will show you the resistance of the resistor.

If it shows 1 in a multimeter, that means this is not in the range you selected, now rotate the knob towards the different range shown in multi-meter then you are able to check on the screen.

### FIND RESISTANCE BY ITS COLOUR CODE

##### b) First write from bottom to top VIBGYOR eliminate I, then write black (B) at top and white (W) at bottom. Then brown colour (B) (dark colour) under black and grey (G) above white.

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CAPACITOR IN SERIES AND CAPACITOR IN PARALLEL

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