DE4401 Electrical and Electronics Principles 1
APTE 5601 Electrical and Electronics Principles
Lab 3
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Question 1
Analyse the following circuit using:
a) Branch current method
b) Loop current method ** optional for BAT students
c) Node Voltage method
d) Multisim simulation software.
Conclusion (how to the simulation compare with calculation):
………………………………………………………………………………………………..
………………………………………………………………………………………………..
………………………………………………………………………………………………..
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Question 2
Analyse the following circuit using:
a) Branch current method
b) Loop current method
c) Node Voltage method
d) Multisim simulation software.
Conclusion (how to the simulation compare with calculation):
………………………………………………………………………………………………..
………………………………………………………………………………………………..
………………………………………………………………………………………………..
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Branch current method
Steps to follow for the “Branch Current” method of network analysis:
1. Choose a node and assume directions of currents.
2. Write a KCL equation relating currents at the node.
3. Label resistor voltage drop polarities based on assumed currents.
4. Write KVL equations for each loop of the circuit, substituting the product IR for E in
each resistor term of the equations.
5. Solve for unknown branch currents (simultaneous equations).
6. If any solution is negative, then the assumed direction of current is wrong.
7. Solve for voltage drops across all resistors (V=IR).
Loop Current Method
Steps to follow for the “Loop (Mesh) Current” method of network analysis:
1. Draw currents in loops of circuit, to account for all components.
2. Label resistor voltage drop polarities based on assumed directions of loop currents.
3. Write KVL equations for each loop, substituting the product IR for E in each resistor
term of the equation. Where two mesh currents intersect through a component,
express the current as the algebraic sum of those two mesh currents (i.e. I1 + I2 if the
currents go in the same direction through that component or I 1 - I2 if not.)
4. Solve for unknown loop currents (simultaneous equations). If any solution is negative,
the assumed current direction is wrong.
5. Algebraically add loop currents to find current in components which share multiple
loop currents.
6. Solve for voltage drops across all resistors (V=IR).
Node Voltage Method
Steps for Node Voltage method:
1. Mark nodes (A, B, C, G).
2. Select a reference (ground) node.
3. Assume the direction of currents. Mark the voltage polarity across each
resistor, consistent with assumed direction of current.
4. Formulate a Kirchhoff’s Current Law (KCL) equation for each no nreference
node.
5. Express all branch currents in terms of voltage drops on components (e.g.
resistor in the branch) by using relationships such as Ohm’s law ( I = V/R)
and the rule for the voltage in parallel branches (“ all parallel branches have
the same voltage”).
a. Resulting equations are now expressed in terms of unknown principal
voltages.
6. With the equations from step 5, go back to the KLC equations from step 4.
Simplify the equations to put them in standard form.
7. Solve the system of equations to find principal node voltages.
8. Next, find all voltage drops and currents in the branches.
a. Negative value for voltage means current is flowing opposite to the
assumed direction and the actual polarity of the voltage is the reverse
of the assumed signs.
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Ohm’s law
Kirchhoff’s current law (KCL)
Kirchhoff’s voltage law (KVL)
Three resistors in series
Three resistors in parallel
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