Resistance:
Electrical resistance describes how an electrical conductor (a wire) opposes the flow of an electrical current (flow of electrons). To overcome this opposition a voltage (a energy) must be dropped (used) across the conductor (wire). Resistance can be described by ohms law:
Ohms Law: R = V / I (Resistance = Voltage / Current) (resistance measured in ohms)
where:
Voltage [V]= the energy lost across an component (voltage measured in volts).
Current [I] = the charge (electrons) flowing through an component (current measured in Amps).
Electrical resistance can be thought of as sticking your hand out a car window. The faster [current] you drive the harder the wind presses [resistance] against you hand and therefore it takes more energy [voltage] to hold your hand steady.
When trying to overcome electrical resistance, the electrical energy lost is turned into heat. This is how the elements of a household stove, toaster, and fan heater work. Because of the vacuum in a light bulb, the electrical energy lost is instead turned into light. It can be seen that electrical resistance plays a large role in modern life.
Resistor:
The resistor is the most common electronic component and is used to limit and/or control the voltage and current in an electronic circuit. Resistors are carefully manufactured to provide a predetermined value of electrical resistance which may range from 0.1 ohms to 100,000,000 ohms, depending on the application. The physical size of a resistor also varies dependent on the amount of power passing through the resistor, given by:
P = V x I (Power = Voltage x Current) (power measured in watts)
There are also many types of resistors including:
· Variable Resistor - changes resistance when its shaft is rotated (volume knob on a stereo).
· Thermistor - changes resistance when the temperature changes (used in a thermostat).
· Light Dependant Resistor (LDR) - changes resistance when the lighting changes (used in children's night-lights).
Resistor Example:
An LED is a small red light (such as the one on the front of most TVs) and requires 2.0 volts and 0.02 amps to operate correctly. If we connected that LED up directly to a 12 volt battery, the voltage would be too high, and too much current would flow… the LED would blow up. We need to use a resistor to limit the voltage and current.
But which value of resistance should the have resistor? Uses ohms law:
R = V / I = (12.0 - 2.0) / 0.02 = 500 ohms
(Note: the voltage across the resistor is the battery voltage minus the voltage we want across the LED)
But which value of power should the resistor be capable of handling?
P = V x I = (12.0 - 2.0) * 0.02 = 0.2 Watts
In an electronic circuit power supply voltage is generally fixed. Resistors is a current limiter for correct devices polarization.
resist flow of current
current limiter
It depends on the purpose for installing the resistor. If the intent is to decrease current flow, the resistor must be connected in series with the load. If the purpose is to increase current flow, the resistor must be connected in parallel with the load. To connect a resistor in series, connect the resistor to one side of the power source, in line with the load. This will decrease circuit current flow. To connect a resistor in parallel, connect the resistor between the positive and negative sides of the power source, which will effectively connect the resistor across the load . This will increase current flow through the circuit. However, before connecting a component in parallel, make sure the increase in current flow will not exceed the current rating of the circuit or fuses/breakers will blow.
if not disconnected you will measure the resistance of the circuit in parallel with the resistor.
It is used to vary the voltage/current flow in a circuit.
describe how to use starting resistors to star a DC motor
a resistor
The purpose of colored bands on a resistor is to tell whoever is installing the resistor the amount of resistance that particuliar resistor has.
The TBA820 is a 2 watt general purpose amplifier integrated circuit, not a resistor.
because without using capacitor or resistor in a circuit,it cant be complete.Resistor is used to protect the circuit by giving a certain amount of voltage.Capacitor is used to charge and discharge purpose.
what does a resistor in an ampliflyer circuit
No. It will not serve its intended purpose.
It depends on the purpose for installing the resistor. If the intent is to decrease current flow, the resistor must be connected in series with the load. If the purpose is to increase current flow, the resistor must be connected in parallel with the load. To connect a resistor in series, connect the resistor to one side of the power source, in line with the load. This will decrease circuit current flow. To connect a resistor in parallel, connect the resistor between the positive and negative sides of the power source, which will effectively connect the resistor across the load . This will increase current flow through the circuit. However, before connecting a component in parallel, make sure the increase in current flow will not exceed the current rating of the circuit or fuses/breakers will blow.
how connect a variable resistor to circuit
There isn't anything "scientific" about this simple series circuit. If you've got a variable resistor (a potentiometer) and a diode in series, you have a simple series circuit with the two components in it.
if not disconnected you will measure the resistance of the circuit in parallel with the resistor.
In a bridge circuit the unknown resistor is compared to the rheostat. When the meter across the bridge reads in the middle the unknown and the rheostat are the same value.
Any part of a circuit that has a voltage drop across it is a resistor.
A resistor.