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Table of contents
Chapter 2 ..................................................................................................................... 1
1-The Resistor: .................................................................................................................... 1
2-Using the Ohmeter: .......................................................................................................... 2
3- The Variable Resistor: .................................................................................................... 3
4-Resistance in the series circuit: ........................................................................................ 4
5-Using the current meter: .................................................................................................. 5
6-Current in the series circuit:............................................................................................. 6
7-Using the Voltmeter: ....................................................................................................... 8
8-Voltage in the series circuit: ............................................................................................ 9
9-Resistance in the parallel circuit: ................................................................................... 10
10-Current in the parallel circuit: ...................................................................................... 11
11-Voltage in the parallel circuits: .................................................................................... 12
12-Power Calculations: ..................................................................................................... 13
Pt = PR1 + PR2 ................................................................................................................. 14
13-Voltmeter loading: ....................................................................................................... 15
14-Resistance in the combination circuit: ......................................................................... 16
15-Current in the combination circuit: .............................................................................. 17
16-Voltage in the combination circuit: ............................................................................. 18
17-The short circuit: .......................................................................................................... 19
18-The open circuit: .......................................................................................................... 20
Chapter 3 ................................................................................................................... 21
Switches: ........................................................................................................................... 21
Chapter 4 ................................................................................................................... 22
Thevenin’s Theorem: ........................................................................................................ 22
Chapter 5 ................................................................................................................... 23
The Wheatstone Bridge: ................................................................................................... 23
Electricity & Magnetism
Lab Report#2
Chapter 2
1-The Resistor:
Materials Required:
A small quantity of resistors of various resistances and power values.
Color Code
Green
Brown
Orange
Brown
Blue
Brown
Orange
Red
Red
Brown
Green
Brown
Brown
Black
Orange
Blue
Grey
Green
Black
Red
Violet
Black
Brown
Black
Red
Red
Black
Red
Orange
Red
Red
Yellow
Brown
Yellow
Brown
Orange
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Coded R Value
Ω
5100
1000
330
100
68000
1500
3000
220000
270
100000
510
10000
Tolerance
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
5%
Table 1:Resistors Values
Self Evaluation:
1.
2.
3.
4.
5.
The power rating of most resistors is fewer than 3 watts and is identified by the
size of the resistor.
Another word for resistance is opposition.
The purpose of a resistor is to oppose current flow.
No, a 492 ohm resistor can not be used for a 470 ohm 5% resistor.
Resistors are usually up-rated by 50 - 100% .
-1-
Electricity & Magnetism
Lab Report#2
2-Using the Ohmeter:
Materials Required:
-Resistors used in the previous exercise.
-DMM.
Procedure:
#
1
2
3
4
5
6
7
8
Color Coded
Green
Brown
Orange
Blue
Red
Brown
Green
Brown
Brown
Black
Orange
Grey
Violet
Black
Brown
Black
Red
Red
Black
Orange
Brown
Yellow
Brown
Orange
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Gold
Color
Coded
Value
5100
1000
330
68000
270
100000
510
10000
Measured
R
Ω
5030
980
327.4
66000
261.4
38500
510
9730
R Within
Tolerance
1.372549
2
0.7878788
2.9411765
3.1851852
61.5
0
2.7
Table 2:Measured resistors within tolerance
Self Evaluation:
1- We have used DM-332.
2- First we select the Ohm range of our choice and we connect the terminals of
the meter to the opposite ends of the resistor.
3- The digital meter because with this meter we get no errors and it is more
specific than the analog meter.
4- No, because resistance of the wires in the circuit and other
components would affect it.
5- No, because the meter needs a voltage source to measure the resistance so we
cannot measure the resistance in a power –on circuit. The circuit voltage
would cause incorrect reading.
-2-
Electricity & Magnetism
Lab Report#2
3- The Variable Resistor:
Materials Required:
-ACT-1
-DMM
-Potentiometer, any value, non linear taper
Procedure:
1.
2.
3.
4.
R22 = 93.6 Kohms
R21 = 9.6 Kohms
Resistance between the central terminal and the left end terminal:
R1=45 Kohms.
Resistance between the central terminal and the right end terminal:
R2=51 Kohms.
RT= R1+R2=96 Kohms.
R22 is linear.
Self Evaluation:
1.
A potentiometer has 3 terminals.
2. First of all , we slide or rotate the pot, if there is a grainy feel the pot is
probably wire-wound. If it slides smoothly, then we have an element potentiometer.
If part of the travel is smooth and part rough, it is a bad resistor.
3. For a non-linear pot, we can realize a slow change in resistance while approaching
one end of the element, and rapid change while approaching to the other end. But for
a linear pot , the change is the same for both ends.
4. There are too many ways for finding the total resistance of a pot: we could turn the
shaft and measure between 2 connections or add both resistances measured between
the center and both end terminals.
5.
The most typical tolerance value for variable resistors is 5%.
-3-
Electricity & Magnetism
Lab Report#2
4-Resistance in the series circuit:
Materials Required:
-Two 1000 resistors- ¼ watt.
-Ohmmeter.
-ACT-1.
-Connecting wire –22 gauge solid.
Procedure:
Measured R1(Ω)
Measured R2(Ω)
989
1939
1002
1002
1002
1098
Measured
RT(Ω)
1991
2963
2088
Table 3:Total resistance values
Self Evaluation:
1.
2.
3.
A circuit contains elements such as resistors, batteries, diodes…
A series circuit has only one path for the current flow.
Current moves from the negative pole to the positive one of any power
source.
4. The total resistance of a series circuit is found by adding all resistances of the
circuit. Rt=R1+R2+R3+……
5. RT = 10 + 2.7 + 0.47 + 1500+ 47 = 1500060.17 K
-4-
Electricity & Magnetism
Lab Report#2
5-Using the current meter:
Materials Required:
-Current meter.
-ACT-1.
-1K ¼ watt resistor.
Procedure:
Figure 1:Experimental circuit 1
3.
The current is: 11.63 mA , or 11,630 uA , or 0.1163A.
Self Evaluation:
1. The current is the movement of electronic charges ( or electrons).
2. Ampere (A) , mA , μA.
3. The meter current ranges 5, 10, 15.
4. In series.
5. The safety rules for using the current meter :
- The circuit must be broken and the current meter must be inserted into
the break.
- Connect the positive lead to the point nearest the positive terminal and
the negative lead to the point nearest the negative terminal.
- Begin the measurement with the meter set to a range known to be
greater than the current to be measured.
6.
Convert the following values:
3 mA = 0.003 A
0.019 A = 19mA
0.000043 A
3.423 μA
-5-
= 0.043 mA
= 0.000003423 A.
Electricity & Magnetism
Lab Report#2
6-Current in the series circuit:
Materials Required:
- Current meter (DMM)
- ACT-1
- Resistors 3, 1K ¼ watt.
Procedure:
1.
Figure 2:Current in the series circuit
2.
4.
5.
6.
7.
8.
9.
10.
12.
Point A= 3.9 mA.
Point B= 5.84 mA.
Point C: 11.68 mA.
Circuit resistance: 3
Kohms.
Circuit resistance: 2,97 Kohms.
Circuit xurrent is determined by the circuit resistance which is 3 Kohms
(calculated) and 2,97 Kohms (measured).
The value 3 Kohms (calculated) is more accurate.
Circuit current is It= V/R=12/3=4 mA
The measured value of the current and the calculated one differ slightly due
to the error that may occur in the DMM.
R is inversely proportional to I .
I= V/R.
13.
Figure 3:Variable power supplied + resistor
-6-
Electricity & Magnetism
14.
15.
16.
17.
Lab Report#2
Measured circuit current: 7.2 mA or 0.0072 A.
The current is 3 mA.
V is proportional to I (V=R I).
It=7.3 mA at 7.5 V and 3.71 mA at 3.75 V
Self Evaluation:
1,2,3 . V=RI , I=V/R ,R=V/I
4. Calculate the following :
Circuit V
12 V
24 V
120V
5. A.
B.
C.
D.
Circuit R
27 KΩ
10 Ω
47 KΩ
Circuit I
0.44 mA
2.4 A
0.00255 A
When V is doubled , I is doubled.V=RI
When V is reduced to 1/3 ,I is reduced to 1/3.
When Rt is tripled ,I is reduced to 1/3.I=V/R
When Rt is halved ,I is doubled.
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Electricity & Magnetism
Lab Report#2
7-Using the Voltmeter:
Materials Required:
-Voltmeter (DMM)
-ACT-1.
Self Evaluation:
1.
3.
4.
The voltmeter ranges: 400mV, 4V,40V,400V.
The voltmeter is connected in parallel in the circuit.
The connection made with the correct polarities means that the positive
terminal should be connected to the point nearest the positive source, and
the negative terminal should be connected to the point nearest the negative
source.
5.
Convert the following:
1.6 V = 1,600 mV = 1,600,000 μV = 0.0016 kV
1236 V = 1.236 kV = 0.001236 MV
0.123 kV = 123 V = 0.000123MV
-8-
Electricity & Magnetism
Lab Report#2
8-Voltage in the series circuit:
Materials Required:
-DMM
-ACT-1
-Resistors 3, 1 k ¼ watt, 1, 2.2 k ¼ watt.
Procedure:
1.
Figure 4:Voltage in the series circuit
2.
VR1 = 3.8 V
VR2 = 3.8V
The sum of the three voltages is:11.4V.
3. The circuit current is: 3.93 mA.
4. The applied voltage is: 11.6 V.
5. The voltage across each resistor:
VR1=3.93 V
VR2 =3.93V
VR3 = 3.8 V
VR3 = 3.93 V
7.
VR1 = 3.72 V
VR2 = 8.07V
The sum of the two voltages is:11.79 V.
8. The measured voltage is:11.8 V.
9. The circuit current is: 3.7 mA.
10. The current drop across each resistor:(Vi=R * I)
VR1 = 3.72V
VR2 = 8.07V
Self Evaluation:
1.
2.
We obtained the total voltage across the circuit.
The total voltage is divided into the circuit across each resistor respecting ohm’s
law:V=RI
4. Calculate the following:
Volts
0.88 V
56 V
Ohms
2200
10000
6. VT = VR1 + VR2 + VR3 + ….
-9-
Amps
0.0004 A
5.6 mA
Electricity & Magnetism
Lab Report#2
9-Resistance in the parallel circuit:
Materials required:
-Ohmmeter (DMM).
-Resistors, 1k and three others of assorted values.
-ACT-1.
Procedure:
Measured
Values
R1 = 1013
R2 = 1013
R1 = 1013
R2 = 1013
R3 = 1013
R1 = 324
R2 = 2152
R3 = 1013
Parallel
Combination
2, 1k
Resistors
3, 1k
Resistors
3 different
Resistors
Measured
RT
498Ω
Calculated
RT
506.5 Ω
331.2 Ω
337.6 Ω
221Ω
220.34Ω
Self Evaluation:
1- RT = R/ #of resistors
2- Law of parallel resistor behavior: 1/RT = 1/R1 + 1/R2 + 1/R3 + ….
3- The total resistance:
Circuit #1: 1021.67 Ω
Circuit #2: 5500 Ω
4- There will be more current in a parallel circuit than in a series using the same
resistors.
5- There is many paths (at least two) for current flow in a parallel circuit.
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Electricity & Magnetism
Lab Report#2
10-Current in the parallel circuit:
Materials Required:
-Current meter
-ACT-1
-Resistors 2, 1k and 1, 2.2 k ¼ watt
Procedure:
R1
Measured R1: 988 ohms
Calculated IR1 :10 mA
Measured IR1:10.13 mA
R2
Measured R2: 981 ohms
Calculated IR2 :10 mA
Measured IR2:10.16 mA
R3
Measured R3: 2.1 Kohms
Calculated IR3 :4.5 mA
Measured IR3:4.6 mA
Table 4:Measured current and resistances
VT = 10 V
Calculated RT = 0.4 Ω
Calculated IT = 26.27 mA
Measured IT = 25 mA
Self Evaluation:
1- The total current in a parallel branch is the sum of all the currents in each branch.
2- The individual resistances control the flow of the current.
3- The total resistances and the voltage source control the current in the total parallel
circuit.
4- I=V/R and IT=V/RT
5- The calculations were within the tolerance of the meter.
- 11 -
Electricity & Magnetism
Lab Report#2
11-Voltage in the parallel circuits:
Materials Required:
-Voltmeter (DMM)
-ACT-1
-Resistors 4, ¼ watt of various sizes (1K and up)
Procedure:
1.The ACT-1 positive voltage source is:11.7 V
4.The voltage across the resistor:11.7
6.The voltage across the other resistor is:11.7 V
8.If we add the two resistors to the circuit, The voltage is always 11. 7 V.
Self Evaluation:
1. The voltage is the same in the parallel circuit .
2. The voltage drop across each resistor is equal to the voltage across the source.
3. From the measurements ,the voltage is the same across all the resistances.
- 12 -
Electricity & Magnetism
Lab Report#2
12-Power Calculations:
Materials Required:
-VOM (DMM)
-ACT-1
-Resistors 2, 1 k and 2, 2.2 k ¼ watt
Procedure:
1.Series circuit:
Figure 5:series experimental circuits.
Measurements
Vt = 11.7 V
It = 5.67 mA
VR1 = 6.71V
IR1 = 5.67mA
VR2 = 5.68V
IR2 = 5.67mA
Calculations
Pt = It * Vt
Pt = 0.066 W
PR1 = 0.034 W
Pt = PR1 + PR2
Pt = 0.066 W
PR2 = 0.032 W
2.Parallel circuit:
Figure 6:parallel experimental circuits
- 13 -
Electricity & Magnetism
Lab Report#2
Measurements
Vt = 11.7 V
It = 10.2 mA
VR1 =11.7V
VR2 = 11.7V
Calculations
Pt = It * Vt
Pt = 0.12 W
PR1 = 0.06 W
Pt = PR1 + PR2
PR2 = 0.06 W
Pt = 0.12 W
IR1 = 5.1mA
IR2 = 5.1mA
Self Evaluation:
1. The power dissipation law for series circuit: Pt = PR1 + PR2 + ….
2. The power dissipation law for parallel circuit: Pt = PR1 + PR2 + ….
3. P=VI
4. The total power of the circuit is equal to the power dissipated by every
resistance.
- 14 -
Electricity & Magnetism
Lab Report#2
13-Voltmeter loading:
Materials Required :
-VOM-low sensitivity ; DMM high sensitivity
-ACT-1
-Resistors 2 , 1 Mohms ¼ watt
Procedure:
1-
Figure 7 Voltmeter Loading
2345-
The total circuit current is: 0.006 mA.
The individual voltage drop is VR1= 6 V and VR2= 6 V.
The voltage measured with a low ohms/volt meter across R2 is VR2= 5.48 V.
The voltage measured with a high ohms/volt meter across R2 is VR2=5.48 V.
Self Evaluation:
1- The voltmeter is always connected in parallel with the component when a
voltage measurment is being made.
2- 1/R (eq) =1/R(of component) + 1/R (of voltmeter).
3- The internal resistance of a meter with a sensitivity of 10,000 Ω /V and set to
the 2.5 volt range is 0.00025 Ω.
4- No, the meter in question3 is not a very good meter for making voltage
measurements since the meter have a minimum of 1MΩ as Ω/V
rating.
5- BY using a higher value for the resistance.
- 15 -
Electricity & Magnetism
Lab Report#2
14-Resistance in the combination circuit:
Materials Required:
-VOM (DMM)
-ACT-1
-Assorted resistors ¼ watt
Procedure :
2- The calculated equivalent resistor is 2666.7 ohms
3- The measured equivalent resistor is 2650 ohms
Self Evaluation:
1- In parallel 1/R (eq) = 1/R1 + 1/R2 +1/R3 +…
In series R (eq) = R1 + R2 + R3 + R4 +…
2- Find the equivalent resistance of series combination first, then the equivalent
resistance for the parallel and then we apply the laws stated in part one depending on
whether they are connected in series or in parallel
3- The equivalent resistance is 71.72 KΩ
4- No due to some imprecision factors as the resistance of the wires , the
resistance of the measurement materials used
Figure 8: Resistances in the combination circuit.
- 16 -
Electricity & Magnetism
Lab Report#2
15-Current in the combination circuit:
Material Required:
-VOM (DMM)
-ACT-1
-Resistors 4, 1kohm ¼ watt and other assorted values
Procedure:
1 & 2:
Resistor Number
R1
R2
R3
R4
Calculated (I)
4.67 / 1000
2.3 / 1000
3.9 / 1000
4.6 / 1000
Table 5:Current values in the combination circuit
- 17 -
Measured (I)
4.69 / 1000
2.35 / 1000
3.8 / 1000
4.69 / 1000
Electricity & Magnetism
Lab Report#2
16-Voltage in the combination circuit:
Materials required :
-
Voltmeter (DMM)
ACT-1
Resistors 4 ,1 kohms ¼ watt
2 - RT=2500 Ω
3 – IT= 4.8 mA
4 –VR1 = VR2= VR3 = VR4
5 – The measured voltage drop is VR1= 4.84V , VR2=2.42V, VR3 = 2.42 ,VR4 = 4.84
Self Evaluation
-
The voltage is equal across the elements connected in parallel is inversely
proportional in series circuit
You can find the equivalent resistance of R2 and R3 and then find the voltage drop
across the equivalent resistance which will be equal to the voltage drop across each.
Yes.
- 18 -
Electricity & Magnetism
Lab Report#2
17-The short circuit:
Materials Required
- Voltmeter , Ohmmeter , Current Meter (DMM)
- ACT-1
- Resistors3, 1Kohms , ¼ watts
Procedure :
2- The total current IT = 4.13 mA
3- Voltages measured = VR1=4.13 V , VR2= 4.13V , VR3= 4.13V.
4- Resistances measured = Rt=2.967 Kohms
6-Measured RT=1.978 Kohms
8-Measured IT= 6.17 mA
9-Voltage measured VR1=6.19V , VR2 =0 V , VR3= 6.21V
Figure 9:short circuit
Self Evaluation
1- A short circuit is simply a connection in parallel with a certain device allowing the
current not to pass through that device.
23- When the wire was connected no current passed through the resistance R2 therefore
no voltage drop could be noticed across it
45- since I=V/R and after R2 has been shorted the total resistance dropped therefore I
increases.
- 19 -
Electricity & Magnetism
Lab Report#2
18-The open circuit:
Material Required:
-DMM
-ACT-1
-Resistors3, 1 Kohms ¼ watt
Procedure :
1-
Figure 10: closed circuit
2- It=35.93 mA.
3- VT=12.42 V
4- VR1=12.29V , VR2=12.29V , VR3=12.28V
5- RT=329.4 ohms
8- IT=24.26 mA.
9- VT=12.39 V
10- VR1=12.3V , VR2=0v , VR3=12.28V
11- RT=494 ohms.
Self evaluation:
2- When R2 was opened the current decreased, and was divided between I1 and I3.
- 20 -
Electricity & Magnetism
Lab Report#2
Chapter 3
Switches:
Materials Required:
1- ACT -1
2- DMM
3- Bulbs 2, 12V @ 35-60 mA bulbs with wire leads or in sockets with wire leads.
4- Switch 1, Double Pole, Double Throw.
5- Diode 1, any type.
Procedure:
1- We have connected the ohmmeter leads across the terminals 1 and 2 of S2 on the
ACT -1.
2- Then we switched S2 from side to side. When the switch is on or closed the
ohmmeter reads no value. But when it’s off or open the ohmmeter reads 0.031 Ω
3- We repeated step 2 with the ohmmeter connected across the terminals 2 and 3 of
S2.
4- Then we have constructed the circuit as seen in figure 11 so that we got a switch
control(one switch).
Figure 11
5- In figure 12 we have two switches as a control over our circuit.
Figure 12
Self Evaluation:
 Single pole- Single throw type used as a light switch.
 To control four different lights, one at a time we used a single switch of type
Double pole- Double throw.
- 21 -
Electricity & Magnetism
Lab Report#2
Chapter 4
Thevenin’s Theorem:
Material Required:
1- DMM
2- ACT -1
3- Resistors 2, 1 K, 1,500 Ω ¼ watt.
Procedure:
1- We have connected the circuit as in figure 13 with leaving RL out of the circuit.
Figure 13
2- The measured voltage across points A and B = 5.84 v
3- Then we removed the power source connections and rewired the circuit as shown
in figure 14
Figure 14
4- The measured Thevnin resistance between A and B= 1985 Ω
5- After that we replaced the power supply and the load resistor as seen in figure 15
Figure 15
The measured voltage from point A to B = 2.94 v.
Self Evaluation:
 The measurements obtained were so close to the calculated values.
 Increasing RL had no effect on VL
- 22 -
Electricity & Magnetism
Lab Report#2
Chapter 5
The Wheatstone Bridge:
Materials Required:
1- DMM
2- ACT -1
3- Resistors 4, 10K
1,1K ¼ watt.
Procedure:
1- Connecting the circuit as in figure 16
Figure 16
2- The calculated voltage from ground to A, and ground to B:
5.89 VA
5.93 VB
The voltage from A to B = 0.04 V.
3- The measured voltage from A to B = 0.002 V.
4- Then we constructed the circuit as in figure 17
Figure 17
5- The calculated voltage from A to B is 0 !
6- The measured voltage from ground to A, and ground to B:
5.89 VA
10.8 VB
the difference in voltage VB-VA = -4.82 V.
7- The measured voltage from A to B = 4.80 V
- 23 -
Electricity & Magnetism
Lab Report#2
Self Evaluation:




There would result a change in the voltage drop across R2 and R4.
The circuit would be unbalanced and the voltage would change.
Yes the A-B measurements matches the calculated ones with a slight
difference.
A good voltmeter.
- 24 -