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Questions and Answers
What happens when devices with different resistances are connected in parallel?
What happens when devices with different resistances are connected in parallel?
Why are electrical devices connected in parallel instead of in series?
Why are electrical devices connected in parallel instead of in series?
What is the effect of connecting devices in parallel on the total resistance?
What is the effect of connecting devices in parallel on the total resistance?
How can three resistors of resistances 2 Ω, 3 Ω, and 6 Ω be connected to give a total resistance of 4 Ω?
How can three resistors of resistances 2 Ω, 3 Ω, and 6 Ω be connected to give a total resistance of 4 Ω?
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What is the purpose of a battery or a cell in an electric circuit?
What is the purpose of a battery or a cell in an electric circuit?
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What happens to the energy provided by the source in an electric circuit?
What happens to the energy provided by the source in an electric circuit?
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What is the effect of connecting devices in series on the total resistance?
What is the effect of connecting devices in series on the total resistance?
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What is the highest total resistance that can be secured by combining four coils of resistance 4 Ω, 8 Ω, 12 Ω, and 24 Ω?
What is the highest total resistance that can be secured by combining four coils of resistance 4 Ω, 8 Ω, 12 Ω, and 24 Ω?
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Why do devices require different currents to operate properly?
Why do devices require different currents to operate properly?
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What determines the total current drawn from a source in a parallel circuit?
What determines the total current drawn from a source in a parallel circuit?
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Study Notes
Electric Circuits and Power
- Electric power (P) is the rate at which electric energy is dissipated or consumed in an electric circuit.
- P is given by the equation: P = VI or P = I²R = V²/R.
- The SI unit of electric power is the watt (W), which is the power consumed by a device that carries 1 A of current when operated at a potential difference of 1 V.
- A larger unit of power is the kilowatt (kW), equal to 1000 W.
Electric Energy and Consumption
- Electrical energy is the product of power and time, and its unit is watt hour (W h) or kilowatt hour (kW h), also known as a "unit".
- 1 kW h = 1000 W × 3600 s = 3.6 × 10⁶ W s = 3.6 × 10⁶ J.
- Electricity consumers pay for the energy used, not for the electrons themselves.
Connecting Devices in Parallel and Series
- Connecting devices in parallel allows each device to operate at its own resistance and current, making it more efficient and flexible.
- In series connection, the total resistance is the sum of individual resistances, and the current through each device is the same.
Resistance and Its Variation
- The resistance of a wire varies inversely with its area of cross-section.
- Tungsten is used almost exclusively for filament in electric lamps due to its high melting point and low vapor pressure.
- Conductors in electric heating devices are made of alloys rather than pure metals to reduce oxidation and increase strength.
Applications of Electric Heating
- Electric heaters convert electrical energy into heat energy, and the rate of heat development is proportional to the square of the current and resistance of the heater.
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Description
Practice problems related to electricity, including lamp ratings, voltage, and energy consumption.
