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Questions and Answers
What is the submultiple unit of power that is 1-thousandth of a watt?
What is the submultiple unit of power that is 1-thousandth of a watt?
- Microwatt
- Megawatt
- Milliwatt (correct)
- Kilowatt
In the context of electric power, which equation represents the relationship between work and time?
In the context of electric power, which equation represents the relationship between work and time?
- Power = work / time (correct)
- Work = power / time
- Power = work + time
- Work = power × time
What is the unit commonly used for large amounts of electrical work or energy?
What is the unit commonly used for large amounts of electrical work or energy?
- Kilowatt
- Kilowatt hour (kWh) (correct)
- Megawatt
- Milliwatt
How is electric cost calculated for an air conditioner operating at 220 volts and 15 amperes?
How is electric cost calculated for an air conditioner operating at 220 volts and 15 amperes?
What is the formula to calculate power in electric systems?
What is the formula to calculate power in electric systems?
What is the equivalent of 1 million watts in standard form?
What is the equivalent of 1 million watts in standard form?
What is the resistance of a device that dissipates 1.2 kW of power when its current is 10 A?
What is the resistance of a device that dissipates 1.2 kW of power when its current is 10 A?
How much current does a 960 W coffeemaker draw from the 120 V power line?
How much current does a 960 W coffeemaker draw from the 120 V power line?
What is the resistance of a 20 W, 12 V halogen lamp?
What is the resistance of a 20 W, 12 V halogen lamp?
In choosing a resistor for a circuit, what is the recommended maximum power dissipation in relation to its power rating?
In choosing a resistor for a circuit, what is the recommended maximum power dissipation in relation to its power rating?
In a circuit where a resistor has a 54 V IR drop and a current of 20 mA, what is the resistance of the resistor?
In a circuit where a resistor has a 54 V IR drop and a current of 20 mA, what is the resistance of the resistor?
If a circuit has a power dissipation of 100 W with a current of 5 A, what is the voltage across the circuit?
If a circuit has a power dissipation of 100 W with a current of 5 A, what is the voltage across the circuit?
What is the cost of using a 450-W microwave for 2 hours if the electricity rate is ₺0.08/kWh?
What is the cost of using a 450-W microwave for 2 hours if the electricity rate is ₺0.08/kWh?
A 60-W light bulb is used for 5 hours per day for a month at ₺0.09/kWh. What is the total cost of using this light bulb for the month?
A 60-W light bulb is used for 5 hours per day for a month at ₺0.09/kWh. What is the total cost of using this light bulb for the month?
If a device operates at 120 W and runs for 8 hours a day at a cost of ₺0.06/kWh, what is the daily cost of operating this device?
If a device operates at 120 W and runs for 8 hours a day at a cost of ₺0.06/kWh, what is the daily cost of operating this device?
What is the total cost of using a computer that consumes 250 W of power for 4 hours per day at a rate of ₺0.10/kWh for a month?
What is the total cost of using a computer that consumes 250 W of power for 4 hours per day at a rate of ₺0.10/kWh for a month?
If a device with a power rating of 90 W runs for 6 hours a day, how much does it cost to operate it for a week at an electricity rate of ₺0.05/kWh?
If a device with a power rating of 90 W runs for 6 hours a day, how much does it cost to operate it for a week at an electricity rate of ₺0.05/kWh?
A refrigerator consumes 400 W of power and runs for 24 hours a day at a rate of ₺0.12/kWh. What is the monthly cost of operating this refrigerator?
A refrigerator consumes 400 W of power and runs for 24 hours a day at a rate of ₺0.12/kWh. What is the monthly cost of operating this refrigerator?
Study Notes
Electrical Power Units
- Milliwatt (mW): One-thousandth of a watt (1 mW = 0.001 W)
- Kilowatt (kW): One thousand watts (1 kW = 1000 W)
- Megawatt (MW): One million watts (1 MW = 1,000,000 W)
Power and Work Relationship
- Power (P) is the rate at which work (W) is done over time (t)
- Formula: P = W / t
Electrical Work and Energy
- Kilowatt-hour (kWh): A unit of energy, equivalent to the amount of energy used by a 1 kW device operating for one hour.
Electrical Cost Calculation
- Cost Calculation: Cost = Power (kW) × Time (hours) × Rate (₺/kWh)
- Example: Air conditioner operating at 220 volts and 15 amperes:
- Power (kW) = (Voltage × Current) / 1000 = (220 × 15) / 1000 = 3.3 kW
- Cost (assuming a rate of ₺0.08/kWh) = 3.3 kW × Time (hours) × ₺0.08/kWh
- Example: Air conditioner operating at 220 volts and 15 amperes:
Power Calculation in Electrical Systems
- Formula: P = V × I
- Where:
- P = Power (watts)
- V = Voltage (volts)
- I = Current (amperes)
- Where:
Resistance Calculation
- Formula: R = V²/P
- Where:
- R = Resistance (ohms)
- V = Voltage (volts)
- P = Power (watts)
- Where:
Power Dissipation in Resistors
- Recommended Maximum Power Dissipation: Ideally, choose a resistor with a power rating at least twice the expected power dissipation in the circuit.
Calculating Current
- Formula: I = P/V
- Where:
- I = Current (amperes)
- P = Power (watts)
- V = Voltage (volts)
- Where:
Electrical Cost Calculations
- General Calculation: Cost = Power (kW) × Time (hours) × Rate (₺/kWh)
- Example: Microwave (450 W) running for 2 hours at a rate of ₺0.08/kWh
- Cost = (450 W / 1000) × 2 hours × ₺0.08/kWh = ₺0.072
- Another Example: Light bulb (60 W) used for 5 hours per day for a month (30 days) at a rate of ₺0.09/kWh
- Total Cost = (60 W / 1000) × 5 hours/day × 30 days × ₺0.09/kWh = ₺0.81
- Calculating Daily Cost: Device (120 W) operating for 8 hours a day at a rate of ₺0.06/kWh
- Daily Cost = (120 W / 1000) × 8 hours × ₺0.06/kWh = ₺0.0576
- Calculating Monthly Cost: Computer (250 W) used for 4 hours per day at a rate of ₺0.10/kWh for a month
- Monthly Cost = (250 W / 1000) × 4 hours/day × 30 days × ₺0.10/kWh = ₺30
- Weekly Operating Cost: Device (90 W) running for 6 hours per day at a rate of ₺0.05/kWh
- Weekly Cost = (90 W / 1000) × 6 hours/day × 7 days × ₺0.05/kWh = ₺0.189
- Monthly Operating Cost: Refrigerator (400 W) running 24 hours a day at a rate of ₺0.12/kWh
- Monthly Cost = (400 W / 1000) × 24 hours/day × 30 days × ₺0.12/kWh = ₺34.56
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Description
Test your knowledge on calculating electrical power, energy consumption, and cost in electrical circuits. Topics include converting watts to kilowatts, multiplying power by hours to get energy, determining the output voltage of a power supply, and calculating the cost of electricity usage.
