Questions:
1. An efficient way to transport electric power is as a three-phase alternating current. What is the typical phase separation (in degrees) between the three phases?
2. When direct current passes through a conductor, the conductor’s material may oppose the current’s flow. This is called resistance. The corresponding opposition for an alternating current is called impedance. It combines the effects of resistance as well as _________. Fill in the blank.
3. The amount of electric charge that a material can store is denoted by its capacitance. To increase the capacitance of an electric circuit, engineers commonly add a device called a capacitor to it. What is the inverse of capacitance called? Though it is rarely used, this quantity is useful in some contexts to understand how well stored charge is released.
4. When capacitance is measured between two objects, like the two plates of a capacitor, it’s called mutual capacitance. When it is measured between an object and the ground, it’s called self-capacitance. What is the value of the earth’s self-capacitance?
5. Name the English physicist who, in the late 19th and early 20th centuries, coined many of the terms like impedance, resistance, capacitance, etc. In his rubric, terms ending in -ance denoted extensive properties and those ending in -ivity (like resistivity) denoted intensive properties.
Visual:
This device is used to increase the voltage and reduce the current in a power line to improve its transmission efficiency. Name it.
Answers:
1. 120 degrees
2. Reactance
3. Elastance
4. 70 microfarad
5. Oliver Heaviside
Visual: Transformer
