- Define electrical work and electrical power
- Calculate electrical energy used in appliances
- Calculate power
- Calculate electricity costs and tariffs.
Skills:
Communication skills
— Take effective notes in class
Strategy: For note-taking, you can use strategies such as the Cornell method, mind maps.
Thinking
— Generate metaphors and analogies
| English | Russian | Kazakh |
| electric circuit | электрическая цепь | электр тізбегі |
| Electrical energy | Электрическая энергия | электр энергиясы |
| do work | совершать работу | жұмыс істеу |
| transfer of energy | передача энергии | энергияның берілуі |
| work done | совершённая работа | жасалған жұмыс |
| rate of energy transfer | скорость передачи энергии | энергияның берілу жылдамдығы |
| cost of electricity | стоимость электроэнергии | электр энергиясының құны |
— Generate metaphors and analogies
Generating metaphors and analogies is useful in science because it helps visualize abstract concepts, improves understanding and memory, supports problem-solving, encourages creative thinking, and allows clear communication of complex ideas.
What are the differences between electrical energy, electrical work, and electrical power? How much money do we spend on electricity?
Electrical work
fig A As part of this circuit, the heart will convert some electrical energy into kinetic energy. The circuit is doing work.
The measurement of voltages in electric circuits has shown us that these deal with the conversion of energy by components. Energy must always be conserved, and electric circuits are no exception to this. When components convert electrical energy into other useful forms, they can be considered to be doing work, as this is defined as a transfer of energy.
Work done has the symbol W, and as the equation defining potential difference includes a term for the amount of energy transferred, E, these two will be the same.
W =E
The equation for potential difference, in rearranged form, gives us:
Table 1. Equation for work
| Equation | Symbol | Units |
 | W=work | Joules (J) |
| V=potential difference | Volts (V) | |
| q=electric charge | Coulombs (C) |
The definition of current, in rearranged form, is the equation
Table 2. Equation for charge
| Equation | Symbol | Units |
 | q=electric charge | Coulombs (C) |
| I=current | Amperes (A) | |
| t=time | Seconds (s) |
Combining these will give us the work done by a component in an electric circuit:
Table 3. Equation for work
| Equation | Symbol | Units |
 | W=work | Joules (J) |
| V=potential difference | Volts (V) | |
| I=current | Amperes (A) | |
| t=time | Seconds (s) |
In fig B, If the bulb lights up for 4.85 seconds, how much work has the bulb done?
| Step 1: Identify the given information. t = 4.85 J V = 7.06 V I = 1.45 A Step 2: Identify the missing variable. W= ? | Step 3: State the formula
Step 4: Substitute the values and calculate.
W=49.6 J |
A student sets up a circuit using a power supply. The voltmeter in the circuit reads 12.0 V, and the ammeter reads a current of 2.5 A. If the circuit does 4500 J of electrical work while the light bulb is on, how long was the power supply running? Give your answer in seconds and minutes.
Step 1: Identify the given information.
W = 4500 J
V = 12.0 V
I = 2.5 A
Step 2: Identify the missing variable.
t= ?
Step 3: State the formula and rearrange it.
The standard formula is:
To isolate t:
Step 4: Substitute the values and calculate.
t=150s=2.5 min
Sources:
- Hudson, M. (2015). Edexcel AS/A level physics 1. Pearson Education Limited.
- Gemini. (2025). Response to a prompt to draw an electric circuit and create a working example. https://gemini.google.com/
Electrical work
ATL skill
Communication skills: Take effective notes in class
Take notes by Cornell method to help you answer these guiding questions:
- What is ‘electrical work’?
- What is the unit of the electrical work?
- What is the formula for calculation of electrical work?
Changes in Electrical Work
- State the definition of electrical work.
- Match each physical quantity with the correct unit. Some units may be used more than once.
Describe what happens to the amount of electrical work if the current or voltage changes.
- Put the elements in the correct order to explain why increasing the resistance in a circuit can change the amount of electrical work done.
Power
Power, P, is the rate of transfer of energy, or the rate of doing work. In an electrical circuit, the energy is dissipated by a component. The mathematical definition is:
Table 1. Equation for power
| Equation | Symbol | Units |
 | W=work | Joules (J) |
| t=time | Seconds (s) | |
| P=power | Watts (W) |
Incorporating the equation for work in a circuit from above:
Table 2. Equation for power
| Equation | Symbol | Units |
 | P=power | Watts (W) |
| V=potential difference | Volts (V) | |
| I=current | Amperes (A) |
Cost of electricity
The electricity board metres in homes, offices and other buildings show how much electricity was used in the building. Readings on the meter (fig 1) give the total amount of energy supplied in “units”. The board meters use kilowatt-hours (kW-h) as the unit of electrical energy. The Electricity Board determines the price for
each unit. To calculate the cost of electricity, the price per unit is multiplied by the total amount of electricity used:
Cost of the electricity in the World
https://worldpopulationreview.com/country-rankings/cost-of-electricity-by-country
A toaster is connected to a 220 V supply and draws a current of 3 A for 10 s. Calculate the electrical work done. Problem: A toaster is connected to a 220 V supply and draws a current of 3 A. Calculate its power. Step 1: Identify the given information 𝑉=220V 𝐼=3A Step 2: Identify the missing variable 𝑃=? Step 3: State the formula Step 4: Substitute the values and calculate P=220*3=660 W A 100 Ω resistor is connected to a 12 V battery. Calculate the electrical power. Step 1: Identify the given information 𝑉=12 V 𝑅=100Ω Step 2: Identify the missing variable 𝑃=? Step 3: State the formula Step 4: Substitute the values and calculate P=1.44 W An electric heater with Step 1: Identify the given information P=2kW t=5h/day*30days=150h Tariff=25 KZT /kWh Step 2: Identify the missing variable Cost=? Step 3: State the formula Step 4: Substitute the values and calculate E=2×150=300 kWh Cost=300×25 Cost=7500 KZT Sources:
a power of 2 kW is used for 5 hours per day for 30 days. The electricity tariff is 25 KZT per kWh. Calculate the total cost of electricity.
ATL Communication skills: Take effective notes in class Take notes by Cornell method to help you answer these guiding questions: 1.What is ‘power’? 2.What is the unit of the power? State the correct terms for each clue in the crossword below. Use your knowledge of electrical work, power, current, voltage, and resistance to complete the puzzle. A family in Kazakhstan receives their monthly electricity bill and is surprised that it is very high. They believe: Table 3. Data of appliances Electricity cost: 30 KZT per kWh Analyse the appliances (table 1): Identify patterns:
“The appliance that works the longest always costs the most.”Appliance Power (W) Time used
per day (h)LED light bulb 10 8 Refrigerator 150 24 Electric kettle 2000 0.5 TV 100 5 Laptop 60 6