• [1] Find the voltage if the resistance is 2K

• [2]Find the Resistance if the current is 150mA and the voltage 0.2V

• [3]Find the voltage if the current is 0.2 A and the resistance is 5Ω𝝁

Note, k x 103 ,m x10-3 , x 10 𝝁 -6

Practical Skills Ev LEARN THESE

LINK Absolute Uncertainty (Absolute Error)

The absolute uncertainty (usually called absolute error - but "error" connotes "mistake", and these are NOT mistakes) is the size of the range of values in which the "true value" of the measurement probably lies. If a measurement is given as 25.4 ±0.1g, the absolute uncertainty is 0.1 g.

G482 L19 Circuit Revision

LO

1. Review Kirchhoff's laws2. Practice using Kirchhoff's 1st ,2nd Laws and Ohms equation

in combined questions. By doing Questions 3. Be able to measure electrical values by construction of

series and parallel circuits. By making and testing circuits.4. Circuit characteristics: correct assembly of series and

parallel resistive circuits using up to three resistors in series, parallel and series – parallel combination; calculation of resistance. By using calculations.

Starter1 : ReminderWhat are Kirchhoff’s laws ?

Practice: Find I1,I2 and I3

Resistors in Series and Parallel Current and Voltages

Review Questions:For the circuits below, what are the unknown p.d.’s and the currents? Show your working

Resistors in Series and Parallel Current and Voltages

Review Questions:For the circuits below, what are the unknown p.d.’s and the currents? Show your working

Combination Questions Using 1st,2nd Ohms Equation• Find V , R ,I1 ,V1 then V2

3 Practice Questions

Combinations of Resistors

• Resistors In Series• When several resistors, eg. R1, R2, and R3 are connected in series, as above:-• the same current, I, passes through each resistor,• the applied voltage, V, is equal to the sum of the voltages across the separate resistors :• => V = V1 + V2 + V3• the total resistance, R, is the sum of the separate resistors.• => R = R1 + R2 + R3

I V

R1 R2 R3

V2 V3V1

©IPK01

R = R1 + R2 + R3

• What single resistor could replace the three resistors shown in the diagram below?

• R = R1 + R2 + R3 • = 1.4 + 2.2 + 3.7 • = 7.3kΩ

k k k1.4 2.2 3.7©IPK01

Resistors In Parallel• When two resistors, e.g. R1 and R2, are

connected in parallel:-

• Remember the voltage across each resistor is the same, V,

• The total current, I, is equal to the sum of the currents in the separate resistors,

I = I1 + I2

• The resulting resistance, R, is given by:-

V

I

R1 R2

I2I1

©IPK01

R1

R1

R1

21

• What is the total value ?

10

5

k

k ©IPK01

R1

R1

R1

21

OR R = R1 x R2 / R1 + R2

What do you notice about the total resistance in parallel compared to

the values of the resistors ?

•Its always LOWER !

• Complete G482 L19 Electrical Examination Practice Qs

Homework

• Complete sheet and mark it using Moodle

• G482 L19

• P 132 Q1,2