+
-
In this presentation you will:
 determine how to calculate circuit elements in series connected circuits
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Sunday, March 17, 13

A lamp in a circuit uses electrical energy.
_
1.5 V
+
A voltage applied across the lamp causes a current to flow and energy to be consumed.
A voltmeter is used to measure the voltage across the load.
This is called potential difference and is measured in volts (V) .
A voltmeter is always connected in parallel with the component, as it measures the voltage across it.
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Sunday, March 17, 13

In this series circuit, the voltage
(potential difference) is divided equally between the lamps, as the lamps are identical.
1.5 V
+
In this circuit the cell has a voltage of 1.5 V.
The potential difference across each lamp will be 0.5 V.
V
0.5 V
V
0.5 V
V
0.5 V
As more lamps are added to a series circuit, they will glow less brightly. This is because they share the voltage.
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Sunday, March 17, 13

Current is measured in amps ( A ) using an ammeter .
_
+
A
When measuring the current through a component, the ammeter should always be connected in series with the component.
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Sunday, March 17, 13

In a series circuit, the same current flows through each component.
0.5 A
A
_
+
0.5 A
A
Wherever an ammeter is placed in the circuit, it will give the same reading.
A
0.5 A
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Sunday, March 17, 13

Where should an ammeter be placed to measure the current through a component in a circuit?
A) In series with the component
B) In parallel to the component
C) Across the cell
D) Outside the circuit
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Sunday, March 17, 13

Where should an ammeter be placed to measure the current through a component in a circuit?
A) In series with the component
B) In parallel to the component
C) Across the cell
D) Outside the circuit
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Sunday, March 17, 13

An ammeter is always connected across a component.
Is this true or false?
Answer True or False.
Sunday, March 17, 13
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An ammeter is always connected across a component.
Is this true or false?
Answer True or False.
False
Sunday, March 17, 13
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Consider two 1 k Ω resistors in series with a single 1.5 V cell.
We know that the current through the circuit is going to be the same at all points in the circuit.
+
1.5 V
_
V
R
1
1 k Ω
I
R
2
1 k Ω
Electron current flow is shown.
The potential difference across each resistor must be the same, since each resistor has the same resistance and the same current passing through it.
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Sunday, March 17, 13

The current flowing through a resistor can be calculated using Ohm’s Law that relates voltage, current, and resistance.
The source of EMF is a
1.5 V cell.
Therefore, each resistor will have a potential
1.5 V difference of 0.75 V across it.
_
+
V
R
1
1 k Ω
I
R
2
1 k Ω
I =
V
R
I = 0.75 mA
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Sunday, March 17, 13

Two 1.5 k Ω resistors are in series with a 1.5 V cell. If a current of 0.5 mA flows through one resistor, how much current will flow through the other resistor?
A) 0.5 mA
B) 1.0 mA
C) 1.5 mA
D) 3.0 mA
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Sunday, March 17, 13

Two 1.5 k Ω resistors are in series with a 1.5 V cell. If a current of 0.5 mA flows through one resistor, how much current will flow through the other resistor?
A) 0.5 mA
B) 1.0 mA
C) 1.5 mA
D) 3.0 mA
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Sunday, March 17, 13

If I = V / R, what does R equal?
A) R = V / I
B) R = I / V
C) R = I V
D) R = V + I
Sunday, March 17, 13
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If I = V / R, what does R equal?
A) R = V / I
B) R = I / V
C) R = I V
D) R = V + I
Sunday, March 17, 13
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Consider three resistors of values R
1
, R
2
, and R arranged in series with a battery of EMF V.
I
The total potential difference is given by :
R
1
3
V
1
V = V
1
+ V
2
+ V
3
+
The same current (I) flows through all resistors.
V
1
= I R
1
_
V R
2
R
3
V
2
V
3
V
2
= I R
2
V
3
= I R
3
Sunday, March 17, 13
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Resistors in series can be represented by a resistor with a resistance that is equal to the sum of their individual values. I
R
T
= R
1
+ R
2
+ R
3
The total current can be calculated using the relationship shown here:
+
_
V
R
1
R
2
V
1
V
2
V = I R
T
R
3
V
3
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Sunday, March 17, 13

What single resistor could replace two 3 k Ω resistors connected in series?
A) 1.5 k Ω
B) 3.0 k Ω
C) 4.5 k Ω
D) 6.0 k Ω
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Sunday, March 17, 13

What single resistor could replace two 3 k Ω resistors connected in series?
A) 1.5 k Ω
B) 3.0 k Ω
C) 4.5 k Ω
D) 6.0 k Ω
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Sunday, March 17, 13

The power of a component is the rate at which it converts electrical energy into other forms of energy.
In the case of a resistor, the electrical energy is converted into heat.
The power in a resistor can be calculated from the product of potential difference and current:
P = V × I where:
P is the power in watts (W)
V is the potential difference in volts (V)
I is the current in amperes (A)
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Sunday, March 17, 13

In the circuit shown, the power in the resistor is calculated in two stages:
+
20 V
_
I =
V
R
P = V × I = 20 × 0.04 = 0.8 W
A
500 Ω V
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Sunday, March 17, 13

What is the power in a 100 Ω resistor when connected to a 10 V source?
A) 0.1 W
B) 1 W
C) 10 W
D) 1,000 W
Sunday, March 17, 13
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What is the power in a 100 Ω resistor when connected to a 10 V source?
A) 0.1 W
B) 1 W
C) 10 W
D) 1,000 W
Sunday, March 17, 13
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In this presentation you have seen:
 how to calculate voltage, current, resistance, and power in series circuits
End >
Sunday, March 17, 13