Physics- Electric circuits

The amount of electrical charge (measured in joules) per unit charge (measured in coloumbs) is called voltage or potential difference. Voltage is calculated using this equation: Voltage = Current x Resistance  

Example: A circuit has a current of 0.5A and a resistance of 12Ω. Calculate the voltage. 

Voltage = 0.5x12      Voltage = 6V

Current is flow of negatively charged electrons. Current can be calaculated using the equation: Current  = Voltage/Resistance 

Example= A circuit has a voltage of 12V and a resistance of 3. Calculate the current. 

Current = 12/3         Current = 4A

When electrons move through a conductor,l like copper wire,  they frequently collide with each other and the copper atoms. The collisions prevent the electrons from moving freely through the wire- this is the resistance.  It can be calculated as: Resistance= Voltage/Current

When a device transforms energy, it is said to do work. Work is measured in joules, J. Electrical power is, therefore, the rate at which an electrical device, such as a light bulb or motor, changes electrical energy into other, more useful forms of energy, such as light, heat and kinetic energy; so it is the electrical work done per second. Electrical Power, like mechanical or thermal power, is measured in watts, W, where 1W = 1J/s. The electrical power can be calculate as:                         Electrical power = Voltagex Current. 

Example 1: If the current is 5A and the potential difference is 12V, what is the electrical power?

Power = 5 x 6      Electrical power = 60J/s

Example 2: What is the electrical power when the current is 4A and the voltage is 6V?

Power = 4 x 6      Electrical power = 24J/s

Example 3: When the power is 56J/s and the potential difference is 8V, what is the current? 

Current = 56/8     Current = 7A

. Compnents in an electric circuit can be connected in series or parallel

. In series, the components are connected one after another so that all the current passes through each component. 

. In parallel circuits, two or more components are connected to the same points in the circuit, and the current splits so that some flows through each of the components in parallel. 

. Current is measured by an ammeter which is connected in series in the circuit. 

. In parallel circuits, the sum of the currents going into the junction is the same as the currents coming out of the junction. 

. Voltage is measured by a voltmeter connected in parallel across the component of the circuit where the voltage is being measured. 

. In series circuits, the overall voltage is the sum of the voltages across each series component, and in parallel circuits the voltage is the same across each component arranged in parallel

Resistance: R= R1 + R2 (series)   1/R= 1/R1 + 1/R2 (parallel)

Current = Voltage/Resistance  Voltage = Resistance x Current    Resistance= Voltage/Current 

Power = Work done/Time        P= E/t        Electrical power= Voltage x Current

Power= Current x Current x Resistance