The following physical quantities are measuered in
an electrical circuit;
*
Current,:* Denoted
by **I** measured in Amperes (**A**).
*
Resistance ,:*
Denoted by **R** measured in Ohmes ( **W**
) .
*
Electrical Potential Difference ,:*
Denoted by ** V** measured in voltes.(**v**)

The flow of current in an electrical circute is goverened by three basic laws:

1. **Ohm's
Law**

2. **Kirchoff's
Voltage Law **Conservation of Energy.

3. **Kirchoff's
Current Law **Conservation of Charge .

one volte = ( one ampere ) X one (ohm)

Electric current is a measure of the amount of charge which pass through
a point in any given instance of time. Or how

much electricity is going through the wires. Current is measured in
Amperes (amps).

One amp is technically defined as one coulomb of charge passing a point
in one second.

I = q/t

I = current (A or Cs-1)

q = change in charge (C)

t = change in time (s)

Georg Simon Ohm devised a formula that relates the voltage,

current, and resistance of a circuit.

V = I x R

V = Voltage (V)

I = Current (A)

R = Resistance (ohms)

Resistance is a measure of the opposing force which is

applied to electricity in a circuit. The resistance of the wires in
the circuit can be ignored, because

it is very low. Motors, lightbulbs, and heating coils are all examples
of resistors.

How to calculate the total resistance in a series circuits ?

A series circuit is a circuit that has only one pathway.

There are no branches in the circuit, and hence the electricity can

only travel in one route.

The total resistance in

a series circuits is the sum of all the values for each

individual resistor.

$ R_{total } = R_1 + R_2 + R_3 + \cdots + R_n $

How to calculate the total resistance in

a parallel circuits?

Parallel circuits are circuits which have more than one branch, or

pathway which electricity can travel through.

The total resistance is the reciprocal of the sum of the

reciprocals of each resistor.

$ \displaystyle \frac { 1 } { R_{total } } = \frac
{ 1 } { R_1 } + \frac { 1 } { R_2 } + \frac { 1 } { R_3 } + \cdots +\frac
{ 1 } { R_n } $

For circuits with series and parallel sections:

First, For each individual series path, calculate the total

resistance for that path.

Second, using these values, by assuming that each path as a single resiator,
calculate the total resistance of

the circuit.

Break the circuit up into portions of series and

parallel, then calculate values for these portions, and use these

values to calculate the resistance of the entire circuit.

=====================

1. The current does not vary as it passes through each individual resistor.

2. In a series circuit the current is the same at any particular point on the circuit.

3. The voltage in a series circuit, however, does not remain constant.

4. The voltage drops across each resistor.

5. The total voltage drop across all resistors will add up to the voltage

off the power source, eg. a battery etc.

6. In parallel circuits current is spread along the various branches.
The current in one

branch will not be the same as in other branches
(unless of course all the resistances are

the same).

7. The sum of the current in each individual branch will add up to give
the total

current of the circuit.

8. The voltage in parallel circuits is actually the same for each branch,
and equal to the

voltage of the power source.

In series circuits, current is constant, but the

voltage is different, and adds to the total voltage.

In parallel circuits, the voltage is constant, but

the current varies, and adds up to the total current in the circuit.