L5.2: Simple electric circuits

L5.2: Simple electric circuits

Pages 130-140

www.mayarschools.com Copyright © 2021/2022 MAYAR International Schools All rights reserved.

Objectives :

1. Define: Electric current and simple circuit.

2. Identify the directions of conventional current and electron current in simple circuit.

3. Construct and compare between series and parallel

circuits.

4. Solve problems related to series and parallel circuits.

www.mayarschools.com Copyright © 2020 MAYAR International Schools All rights reserved.

What is simple circuit?

- Electric current is a flow of electric

charges.

- Electric circuit is any closed loop or

conducting path allowing electric

charges to flow.

www.mayarschools.comCopyright © 2020 MAYAR

International Schools All rights reserved.

www.mayarschools.comCopyright © 2020 MAYAR International Schools All rights reserved.

Direction of the current in a circuit- Electrons flow from the negative(-)

terminal of a cell through a device to the positive(+) terminal.

Conventional Current flows

From the (+) terminal of a cell through a device to the(-) terminal.

www.mayarschools.com Copyright © 2020 MAYAR International Schools All rights reserved.

Ohm’s Law

Resistance

• Resistance: is an opposition to the flow of current

-Resistance is measured in Ohms (Ω).

• potential difference (voltage) between two points in a circuit is the amount of energy transferred between those points in the circuit

• Potential difference is measure in volts (V)

Ohm’s Law

• Ohm’s law states that current is directly proportional to potential difference (providing the temperature remains constant).

• Voltage = Current x Resistance

V = I x R

https://phet.colorado.edu/sims/html/ohms-law/latest/ohms-law_en.html

www.mayarschools.comCopyright © 2021/2022 MAYAR International Schools All rights reserved.

Ohm’s Law

Question-1

• In the circuit shown, If the current flows in the resistor is 2 A, what is the voltage difference across the resistor?

………………………………………………………………………………………………………………………………………………….....


Ohm’s Law

Q2. A 12V filament light bulb has a resistance of 60Ω. What current flows through the bulb?....................................................................................................

....................................................................................................

....................................................................................................

.....................................................................................................

...


Ohm’s Law

Q3. If the current flows through the bulb in the figure is 0.5A, and the voltage difference across it is 9 V . What is the resistance of the bulb?....................................................................................................

....................................................................................................

....................................................................................................

.....................................................................................................

...


resistance of a wireThe factors affecting

the resistance of a wire are:

• Length• Cross-sectional area (thickness)• Material• Temperaturehttps://phet.colorado.edu/sims/html/resistance-in-a-wire/latest/resistance-in-a-wire_en.html


Series and Parallel circuits

- In a series circuit the current flows in one loop.

-

- If one component breaks, all the other components will stop working

- More bulbs in series will cause the brightness of all the bulbs to decrease

Switches will control all the bulbs together

- The same current (I) flows in all bulbs.

- The voltage across each bulb add up to the voltage across all the bulbs: V= V1+V2

- Total resistance: R total = R1+ R2+…


Series Circuit

Q.4: Series Circuit

In the circuit shown, a 14 v battery is

connected in series with two resistors. 1. What the total resistance of the circuit?…………………………………………………………………………………………………………………………………………………………2. What is the current through the 4 Ω resistor? And through the 3 Ω?

……………………………………………………

……………………………………………………

………………………………………………V = I x R

8= I x 7Copyright © 2021/2022 MAYAR International Schools All rights reserved.

RI = V/RI = 8/7

I = 1.1 A

Series Circuit

Q.5: Series Circuit

In the circuit shown, a 10 v battery is

connected in series with two resistors. 1. What the total resistance of the circuit?…………………………………………………………………………………………………………………………………………………………2. What is the current through the circuit?……………………………………………………

……………………………………………………

………………………………………………V = I x R

8= I x 7 Copyright © 2021/2022 MAYAR International Schools All rights reserved.

RI = V/RI = 8/7

I = 1.1 A

Parallel Circuit• There is more than one path around the

circuit• If one component breaks, the others stay

on• More bulbs added in parallel will be the

same brightness as the original bulb• Same voltage difference across each bulb

(Vs=V1=V2…)• Switches on branches will control bulbs

individually• The total resistance:


Series and Parallel Circuit


Parallel CircuitQ6. In the figure below, the resistances of the light bulbs are: R1= 6 Ω, R2 = 12 Ω, what is the total resistance of the circuit?

………………………………………………………………………………………………………………………………………………………………………………………………………


Parallel CircuitsQ.7:

In the circuit shown:

a. What is the total resistance of the circuit?

……………………………………………………………………………………………………………………………………………………………………………………………………………

(100×100)/(100+100)= (10000/200)=100/2=50 Ω

b. What is the reading of voltmeter1? Voltmeter2? Voltmeter3.

……………………………………………………………………………………………………..

c. Calculate the total amount of current that the battery must supply to this parallel circuit.

……………………………………………………………………………………………………………………………………………………………………………………………………………..


Ammeter Connection

• An ammeter measures current.

• The ammeter is connected in seriesin a circuit.

• A voltmeter measures the potentialdifference (voltage) between twopoints.

• The voltmeter is connected inparallel between two points ofcircuit

Short circuit

• A short circuit is a low resistance path forthe current to follow.

Or

a very easy route for electrons to flow.

• This can result in very hot wires andcreation of a fire risk

L5.2: Simple electric circuits

Documents