The shape of the lesson
By the end of the lesson, learners can
- Count the charge per second: Vary the current and time and read off the charge that has flowed.
- One relation, three uses: From any two of charge, current and time you can find the third.
- Three forms: I = Q ÷ t, Q = It, t = Q ÷ I.
- Units: amperes, coulombs, seconds. One ampere is one coulomb per second.
- Convert first: change any minutes or hours into seconds before using the equation.
One picture every idea returns to
Current is the charge passing a point each second: I = Q divided by t. Rearranged, the charge delivered is Q = I multiplied by t, measured in coulombs. One ampere is one coulomb per second.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, How much, how fast.. Current is not a thing in itself, it is a rate: the amount of charge sweeping past a point every second. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Count the charge per second | Vary the current and time and read off the charge that has flowed. Project tab 2 of the lab (Conductors and charge flow) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: One relation, three uses | From any two of charge, current and time you can find the third. Model the worked example Worked example on the board, one line at a time. | Numbered Heads Together |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 14 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in One relation, three uses, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Numbered Heads Together
Teams of four number off. Put up a question, give the team time to make sure every member can answer, then call a number: that student answers for the team, so nobody can leave the thinking to someone else.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Keep the relation the right way up: I = Q divided by t. | To find the charge, multiply current by time, Q = I t. A coulomb is an ampere-second. |
Current as charge flow (I = Q / t): worksheet
6 questions, 14 marks. Written in the style of the papers; no past paper question is reproduced.
Write the equation linking current, charge and time, naming each quantity and its unit, and state what one coulomb is.
A current of 0.50 A flows for 60 s. Calculate the charge that passes.
A charge of 90 C passes through a lamp in a time of 60 s. Calculate the current.
A current of 3.0 A is needed to deliver a charge of 60 C. Calculate the time for which the current must flow.
A steady current of 0.20 A flows for 5.0 minutes. Calculate the charge that passes, giving your answer in coulombs.
Two wires carry the same charge of 24 C past a point. In wire A it takes 12 s; in wire B it takes 4.0 s.
Calculate the current in each wire, and state which wire carries the larger current.
Answer key and marking notes
- I = Q ÷ t, where I is current (A), Q is charge (C) and t is time (s). ✓
- One coulomb is the charge that passes when a current of 1 A flows for 1 s. ✓
- Q = It = 0.50 × 60
Q = 30 C
- I = Q ÷ t = 90 ÷ 60
I = 1.5 A
- t = Q ÷ I = 60 ÷ 3.0
t = 20 s
- t = 5.0 × 60 = 300 s
Q = It = 0.20 × 300
Q = 60 C
convert minutes to seconds first
- Wire A: I = 24 ÷ 12 = 2.0 A
Wire B: I = 24 ÷ 4.0 = 6.0 A
Wire B carries the larger current. ✓
same charge in less time means a larger current
4 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
A current of 2.0 A flows for 30 s. How much charge passes a point in the circuit?
- A60 C
- B15 C
- C0.067 C
- D32 C
A charge of 120 C passes through a lamp in 60 s. What is the current?
- A2.0 A
- B0.50 A
- C7200 A
- D180 A
How long does it take for 45 C of charge to flow when the current is 1.5 A?
- A30 s
- B67.5 s
- C0.033 s
- D43.5 s
What is the coulomb, the unit of electric charge, equivalent to?
- Aone ampere-second (the charge passing when 1 A flows for 1 s)
- Bone volt per second
- Cone watt-hour
- Done joule per ampere
Quiz key
Q = It = 2.0 × 30 = 60 C. Option B divides the values; C inverts the formula.
I = Q ÷ t = 120 ÷ 60 = 2.0 A. Option C multiplies the values; B inverts the division.
t = Q ÷ I = 45 ÷ 1.5 = 30 s. Option B multiplies the values; D subtracts them.
Because Q = It, one coulomb is one ampere-second: the charge that flows when a current of 1 A passes for 1 s. The other combinations describe different quantities.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.