Ch. 21 Flashcards
(7 cards)
Suppose you charge a comb by rubbing it through the fur on your dog’s back. Do you produce a current when you walk across the room carrying the comb?
Yes. There is a net charge separated and deposited on the comb surface and by moving the comb one place to another you have created an electric current.
An electron moving through a wire has an average drift speed that is very small. Does this mean that its instantaneous velocity is also very small?
No. An electron may have a fairly large velocity at any given time, but because its direction of motion keeps changing-due to its collisions with atoms in the wire- its average velocity is almost zero.
Is it possible to connect a group of resistors of a value R in such a way that the equivalent resistance is less than R? If so, give a specific example.
If two or more of resistors of different or equal resistances is connected in parallel combination, the equivalent resistance is always less than the all resistor in the given network.
What physical quantity do resisters connected in series have in common?
Resistors connected in series have the same current flowing through them.
What physical quantity do resistors connected in parallel have in common?
When the resistors are connected in parallel the potential difference is same across all the resistors. So, the potential difference is the physical quantity common in parallel combination of resistors.
Explain the difference between resistivity and resistance
Resistance- a measure of the degree to which a substance impede the flow of electric current induced by a voltage.
Resistivity - The quantity that characterizes the resistance of a given material is its resistivity.
Consider the circuit shown below in figure x, in which a light of resistance R and a capacitor of capacitance C are connected in series. The capacitor has a large capacitance and is initially uncharged. The battery provides enough power to light the bulb when connected to the battery directly. Describe the behavior of the light after the switch is closed.
The light will shine brightest immediately after the switch is closed. Over time the intensity of the light diminishes and eventually, the light will stop glowing altogether.
