Who developed the electrical circuit rules used in circuits?
Gustav Kirchhoff
What two conservation laws are electrical circuit rules based on?
Conservation of charge and conservation of energy
What is Kirchhoff’s current rule?
The algebraic sum of currents at a junction equals zero
Write the mathematical form of the current rule
ΣI = 0
What does Kirchhoff’s current rule mean physically?
The total current entering a junction equals the total current leaving
Why must current be conserved at a junction?
Because electric charge cannot be created or destroyed
What happens to current when it reaches a junction?
It splits into different branches
Write the junction current equation for three branches
I₁ = I₂ + I₃
What is Kirchhoff’s voltage rule?
The sum of emfs around a closed loop equals the sum of potential differences
Write the voltage rule mathematically
Σε = ΣV
What does Kirchhoff’s voltage rule represent physically?
Conservation of energy in a circuit
Why must the sum of voltages around a loop equal the emf?
Because all supplied electrical energy must be transferred to components
What equation expresses potential difference across a resistor?
V = IR
How can the voltage rule be written using Ohm’s law?
Σε = ΣIR
What happens if you move around a loop opposite to current through a resistor?
The potential difference is considered negative
Why can ammeters often be ignored in voltage calculations?
Because ideal ammeters have negligible resistance
Why can voltmeters often be ignored in circuit calculations?
Because ideal voltmeters draw negligible current
What is meant by a closed loop in a circuit?
A complete path that starts and ends at the same point
What happens if the algebraic sum of voltages in a loop is not zero?
Energy conservation would be violated
What happens if the sum of currents at a junction is not zero?
Charge conservation would be violated
What equation combines Kirchhoff’s voltage rule with Ohm’s law?
Σε = ΣIR
Why are Kirchhoff’s laws useful?
They allow analysis of complex circuits
What is the relationship between emf and potential differences in a loop?
Total emf equals total potential difference
What happens to current in components connected in series in a loop?
The current is the same through each component
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1.1.1 Velocity, Acceleration, Motion Graphs39
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1.1.2 Kinematic equations37
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1.1.3 Adding and resolving vectors38
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1.1.4 Moments32
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1.1.5 Newton’s laws of motion43
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1.1.6 Projectile Motion35
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1.2 Energy, work and power29
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1.3 Momentum25
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3A.1 Wave Basics18
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3A.2 Wave types14
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3B.1 wave phase and superposition14
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3B.2 Stationary waves19
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3B.3 Diffraction15
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3B.4 wave interference14
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3C.1 Refraction15
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3C.2 Total internal refraction18
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3C.3 Polarisation19
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3D.1 Wave particle duality21
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3D.2 the photoelectric effect21
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3D.3 Electron diffraction and interference21
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3D.4 atomic electron energies27
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4A.1 electric circuits24
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4A.2 electrical energy transfer22
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4A.3 current and voltage relationships22
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4A.4 resistivity26
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4A.5 conduction and resistance27
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4A.6 semiconductors33
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4B.1 series and parallel circuits33
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4B.2 Electrical circuit rules25
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4B.3 Potential dividers30
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4B.4 emf and internal resistance30
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4B.5 power in electric circuits36
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practical unit 3119
