Components are chosen based on factors including working properties, environmental impact, function, manufacturing processes etc. It is important to choose a component fit for purpose.

Ohm’s law is one of the most important laws of electrical circuits. It states that the current passing through a conductive material, eg a resistor, is equal to voltage divided by resistance. Ohm’s triangle can be used to remember three important equations:

- voltage (V) - the potential difference between two points, measured in volts (V)
- current (I) - the flow of electricity around a circuit, measured in amps (A)
- resistance (R) - how easily electricity flows through a wire, measured in ohms (Ω)

Sometimes more than one resistor is used in a circuit. To calculate the combined resistance, each resistor’s value should be added together:

Resistance or R_{total} = R_{1} + R_{2} + R_{3}

What is the total value of resistors below?

R_{total} = R_{1} + R_{2} + R_{3}

= 10 + 22 + 2,200

= **2,232 Ω**

- Question
What is the total value of resistors below?

R

_{total}= R_{1}+ R_{2}+ R_{3}= 24 + 31 + 1500

=

**1,555 Ω**

When resistors are placed in a parallel arrangement, the resistors are in parallel - the current is shared between each junction.

Resistance or 1/R_{total} = 1/R_{1} + 1/R_{2} + 1/R_{3}

What is the total resistance for the circuit below?

1/R_{total} = 1/R_{1} + 1/R_{2} + 1/R_{3}

= 1/6 + 1/3 + 1/9

Give them a common denominator:

= 3/18 + 6/18 + 2/18

1/R_{total} = 11/18

Therefore, 11R_{total} = 18

R_{total} = 18/11

= **1.64 Ω**

- Question
What is the total resistance for the circuit below?

1/R

_{total}= 1/R_{1}+ 1/R_{2}+ 1/R_{3}= 1/8 + 1/24 + 1/4

Common denominator:

= 3/24 + 1/24 + 6/24

1/R

_{total}= 10/24Therefore, 24R

_{total}= 10R

_{total}= 10/24=

**0.42 Ω**