# Unit Planner: Electricity

Unit 10: Electrical circuits

Start date:

End date:

Diploma assessment

When will the content be assessed?

Paper 1 x
Paper 2 x
Paper 3 x
Investigation x

Text book reference

Hamper Chapter 6

#### Inquiry: Establishing the purpose of the unit

Transfer Goals
List here one to three big, overarching, long-term goals for this unit. Transfer goals are the major goals that ask students to “transfer”, or apply, their knowledge, skills, and concepts at the end of the unit under new/different circumstances, and on their own without scaffolding from the teacher.

• Current flows through a conductor when there is a potential difference across it
• Resistance is due to interactions between electrons and lattice
• All circuit problems can be solved by applying simple laws

Content
List here the key content that students will know by the end of the unit

• Define conductor and insulator
• define PD current and resistance
• I = nAve
• Ohm's law
• EMF, terminal pd and internal resistance
• Different type of cell
• The simple cct
• Electrical power
• Combinations of components
• Use of ammeter and voltmeter
• Kirchoff's laws
• Potential divider

Skills
List here the key skills that students will develop by the end of the unit.

• Solving cct problems using Kirchoff's laws
• Interpreting cct diagrams
• Connecting ccts
• Measuring I, V and R using multimeter
• Interpreting VI graphs
• Using a circuit simulator

Concepts
List here the key concepts that students will understand by the end of the unit

• Potential goes up and down around a circuit
• Current is due to flow of electrons flowing with constant velocity
• Current is the same for components in series
• Resistance is due to interactions between lattice and electrons
• Battery converts chemical energy to electrical
• Electrical energy is converted to heat in a resistor
• If a battery is short circuited all energy is converted to heat in the internal resistance
• R is a ratio not a rate of change
• Adding resistors in parallel reduces the total in series increases.
• Kirchoff's laws are conservation laws
• An ideal voltmeter has high resistance an ammeter low

Applications
Examples of real world practical applications of knowledge.

• Anything with a battery

#### Action: teaching and learning through Inquiry

Approaches to teaching
Tick boxes to indicate pedagogical approaches used.

Lecture
Simulation x
Small group work (pairs) x
Hands on practical x
Video
Student centred inquiry x

TOK
Examples of how TOK can be introduced in this unit

• An Ohmic conductor is one that obeys Ohm's law and Ohm's law applies to ohmic conductors.
• Analogies; there are no ups and downs in a circuit but we talk about going up and down in potential.
• EMF stand for Electro Motive Force but it isn't a force. How names of things can give the wrong impression. Can EMF be a word in itself?
• Another example of using analogies to explain things that we can't see.
• The whole business about current flowing in the opposite direction to charge flow is an interesting topic. Why do we talk about current instead of electron flow? Imagine that we used a model where current flowed up hill, what would be the point of this model? Would it help us to visualise current?
• The way we say that it is not possible to use the laws of physics to solve the problem of parallel batteries with zero internal resistance implies that its not possible to have a battery without internal resistance is an interesting way of proving that something exists.
• Using Kirchoff's laws to solve circuit problems often results in a lot of simultaneous equations. At what point does physics become maths?
• Can we ever measure a quantity without changing it?

NOS
Examples of how NOS can be introduced in this unit.

• The consistency between all physical models. The same model that we use to explain the states of matter has to also explain electrical resistance.
• Here we use the law of conservation of energy to derive equations for combinations of resistors. Physical laws have far reaching consequences.
• The equations for series and parallel combinations are useful for solving problems but can't always be applied.
• Gustav Robert Kirchhoff (12 March 1824 – 17 October 1887) was a German physicist who contributed to the fundamental understanding of electrical circuits, spectroscopy, and the emission of black-body radiation by heated objects. (http://en.wikipedia.org/wiki/Gustav_Kirchhoff) Physicists often made discoveries in many different areas.
• To verify theory we must do experiments that involve measuring quantities but sometimes those quantities are changed by the act of measurement.

Resources
Video clips, simulations demonstrations etc.

#### Reflections

What went well
List the portions of the unit (content, assessment, planning) that were successful

What didn’t work well
List the portions of the unit (content, assessment, planning) that were not as successful as hoped

Notes/changes/suggestions:
List any notes, suggestions, or considerations for the future teaching of this unit.

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