Class 12 Physics — Chapter 7: ALTERNATING CURRENT

What you'll learn

• ▸Introduction to Alternating Current (AC)
• ▸AC Voltage Applied to a Pure Resistor
• ▸Root Mean Square (RMS) Values
• ▸Power in AC Circuits
• ▸Phasor Diagrams
• ▸AC Voltage Applied to a Pure Inductor

Chapter Summary

--- PAGE 1 --- Chapter Seven ALTERNATING CURRENT 7.1 INTRODUCTION We have so far considered direct current (dc) sources and circuits with dc sources. These currents do not change direction with time. But voltages and currents that vary with time are very common. The electric mains supply in our homes and offices is a voltage that varies like a sine function with time. Such a voltage is called *alternating voltage* (ac voltage) and the current driven by it in a circuit is called the *alternating current* (ac current)*. Today, most of the electrical devices we use require ac voltage. This is mainly because most of the electrical energy sold by power companies is transmitted and distributed as alternating current. The main reason for preferring use of ac voltage over dc voltage is that ac voltages can be easily and efficiently converted from one voltage to the other by means of transformers. Further, electrical energy can also be transmitted economically over long distances. AC circuits…

Practice Questions from this Chapter

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1. Explain alternating current simply. Get Solution →
2. Describe how transformers work? Get Solution →
3. Compare AC versus DC power. Get Solution →
4. What is a voltage that varies like a sine function with time called? Get Solution →
5. What is the main reason mentioned in the text for preferring AC voltage over DC voltage for power distribution? Get Solution →
6. What is the symbol for an AC source in a circuit diagram? Get Solution →
7. In a purely resistive AC circuit, what is the phase relationship between the voltage and the current? Get Solution →
8. What is the average value of alternating current over one complete cycle? Get Solution →

Did you know?

• 💡 Thomas Edison once electrocuted animals to make people fear alternating current.
• 💡 Nicola Tesla imagined a global wireless power system, but it was never built.
• 💡 The electricity in your wall outlet switches direction 100 or 120 times each second.
• 💡 Electricity flows through wires incredibly fast, nearly the speed of light.
• 💡 A single bolt of lightning contains enough energy to power a city for days.

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