l5.2: simple electric circuits
TRANSCRIPT
L5.2: Simple electric circuits
Pages 130-140
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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.
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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.
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International Schools All rights reserved.
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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.
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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
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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?
………………………………………………………………………………………………………………………………………………….....
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Ohm’s Law
Q2. A 12V filament light bulb has a resistance of 60Ω. What current flows through the bulb?....................................................................................................
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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?....................................................................................................
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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
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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+…
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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:
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Series and Parallel Circuit
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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?
………………………………………………………………………………………………………………………………………………………………………………………………………
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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.
……………………………………………………………………………………………………………………………………………………………………………………………………………..
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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