Potential divider circuits can vary the p.d. across an output (e.g a lamp) when connected to a fixed point. These are useful in circumstances such as having a 10V battery but only needing 6V for the task you are about to perform.
Basically, there are two resistors in a series circuit. All you have to do is connect a circuit across one of these resistors. The p.d. into this circuit (which is Vout of the potential divider circuit) can be varied from zero to maximum depending on the resistances of R1 and R2.
This means that the p.d. across each resistor in a potential divider depends on the resistances of the individual resistors...
We can determine Vout by the potential divider equation:
You can also 'load' a potential divider circuit. This refers to adding an additional resistor/component to the Vout part in parallel which overall decreases the total resistance of this part which lowers Vout. A small additional resistance in parallel significantly reduces Vout.
The potentiometer
To vary Vout we can replace one of the fixed resistors with a variable resistor. A potentiometer is a type of variable resistor that has 3 terminals and a sliding contact. If you adjust the contact the p.d. between two of the terminals will vary. Potentiometers are very compact which is useful so they can be used for portable electronic devices etc.
Temperature sensing circuits
To vary Vout we can replace one of the fixed resistors with a variable resistor.
Replacing the variable resistor with a fixed resistor allows Vout to vary depending on the temperature of the surroundings (as temperature increases resistance of the thermistor decreases as thermistors have a negative temperature coefficient).
Light sensing circuits
A similar principle to temperature sensing circuits only replace the variable resistor with an LDR. As light intensity increases, resistance falls.
Basically, there are two resistors in a series circuit. All you have to do is connect a circuit across one of these resistors. The p.d. into this circuit (which is Vout of the potential divider circuit) can be varied from zero to maximum depending on the resistances of R1 and R2.
This means that the p.d. across each resistor in a potential divider depends on the resistances of the individual resistors...
V1/V2 = R1/R2
We can determine Vout by the potential divider equation:
Vout = (R2/(R1+R2)) x Vin
You can also 'load' a potential divider circuit. This refers to adding an additional resistor/component to the Vout part in parallel which overall decreases the total resistance of this part which lowers Vout. A small additional resistance in parallel significantly reduces Vout.
The potentiometer
To vary Vout we can replace one of the fixed resistors with a variable resistor. A potentiometer is a type of variable resistor that has 3 terminals and a sliding contact. If you adjust the contact the p.d. between two of the terminals will vary. Potentiometers are very compact which is useful so they can be used for portable electronic devices etc.
Temperature sensing circuits
To vary Vout we can replace one of the fixed resistors with a variable resistor.
Replacing the variable resistor with a fixed resistor allows Vout to vary depending on the temperature of the surroundings (as temperature increases resistance of the thermistor decreases as thermistors have a negative temperature coefficient).
Light sensing circuits
A similar principle to temperature sensing circuits only replace the variable resistor with an LDR. As light intensity increases, resistance falls.
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