3-ELE-04

Outcomes

• Pupils can use the equation: Q = I × t
• Pupils can identify the direction of movement of charge in a wire, charge in an electrolyte and the direction of flow of conventional current
• Pupils understand the effect of changing the voltage on the current
• Pupils know that the voltage is a measure of the energy per unit charge

Specification References

2.16 understand that current is the rate of flow of charge

2.17 recall and use the relationship between charge, current and time : charge = current × time

2.18 recall that electric current in solid metallic conductors is a flow of negatively charged electrons

2.19 recall that:

• voltage is the energy transferred per unit charge passed
• the volt is a joule per coulomb.

Starter

• Demonstrate potassium permanganate in amonia on filter paper, resting on a slide in an electric field. Alternatively view the movement of ions.

Main Body of Lesson

Class Practical: Electrolysis

• Use this worksheet to plan an experiment to investigate the variables that affect the rate of completely coating a 10p coin with copper - we are concentrating on how voltage affects the rate.
• The pupils make a detailed prediction as to which terminal the 10p should be placed and what the other variables should be set at in order to achieve the quickest coating.
• The pupils observe the coin being coated. After a fixed time interval, maybe 4 minutes, the pupils remove the coin, dry it and reweigh it to find the mass of copper transferred. This is done for a range of voltages. The resulting data shows how increasing the voltage (and therefore the current) affects the mass of copper added; therefore the movement of copper ions.
• In conclusion, the pupils should link increasing the 'voltage' to an increase in current when all other variables are kept constant. Furthermore, they should start to link voltage to the work done (energy) to coat the coin. Indeed if the voltage is increased then the ions are given more energy, move faster and the coin is coated more rapidly.

Plenary

• Class act as charges in a circuit. Which way would they move if they were i) positive ii) negative? What happens in a solid and a liquid?

Homework

• To read pages 176-180 in Complete Physics and to write an analogy for current, voltage and resistance in a series circuit.

Additional Information

Resources Required

• Movement of ions demo with potassium permanganate and amonia.

• Class practical electrolysis kits and 10pence pieces, accurate mass balance

Textbook References

• Complete Physics Pages 174-175.

Safety/Hazards

• High voltages are used to demonstarte the movement of ions. Do not switch on the power supply until the paper has been soked in ammonia.
• The teachers and Pupils should use goggles as there are chemical being used.
• Tweesers should be used to handle copper sulphate and potassium permanganate crystals.
• The teacher should pour out the copper sulphate solution into beakers as the container is heavy - Manual handling.
• Tweezers should be used to handle the coin and was with Ethanol to prevent contact of copper sulphate and ethanol with skin. For more details see the document: The use of ethanol

Electricity Outline

Electricity