D.C circuits

Current in a series circuit

There is only one path for charges to move in a circuit. At every point in the circuit, the same amount of charges passing through it. Therefore current is the same at every point in the circuit

It = I1 = I2

DIsadvantages of series circuit

A fault at any point in the circuit will reak the flow of charge, so there will be no current flowing through the circuit

Potential difference in a series circuit

The sum of the potential difference for components in a series circuit is equal to the potential difference across the whole circuit

effective resistance in series

Re = R1+R2+R3

effective resistence in parallel

1/Re = 1/r1 + 1/r2

Current in a parallel circuit

There are more than one path for charges to move in a circuit. If all the parts have the same resistance, current will be split equally from the main current will be greater in the lower resistence path

Advantage of parallel circuit

A fault in one parallel path will not affect the circuit in another parallel path

Potential difference in parallel circuit

The potential difference across the separate paths of a parallel circuit is the same as the potential difference of the source

Potential divider

Potential divider is used to divide the output voltage in any desired ratio form the input voltage

Vout = r2/r1+r2 x Vinput

Transducers used in potential divders

• Transducers are electrical devices which are able to convert energy from one form to another. THermistors and Light-dependent resistors (LDR) are two examples of transducer

• IN electrical circuits, input transducers are devices that convert non-electrical energy to electrical energy. They respond to change in the environmental such as light, temperature, forces by a change in resistance. THe change in their resistance affect the voltage output in the circuit

Thermistors

• A thermistor is a device which responds to a change in temperature: resistance decreases as temperature increases, and vice versa

Use of Thermistors in potential dividers

• can be used as input transducers in potential dividers

• When the temperature in the surroundings increase, the resistance of the thermistor decreases. Thus voltage decreases

• It will result in the increase of the voltage output in the resistor

Light dependent resistors (LDR)

• Device which repoonds to a change in light intensity

• its resistance decreases as light intensity increases

• Mainly used in light detector such as burgarlar alarm systems