1. Current, Resistance Chapter 24 24.1 Current
24.2 Conductivity and Resistivity
24.3 Resistance and Ohm’s law
24.4 Electric power

2. Question: When you turn the ignition key in the car, you complete a circuit from the negative battery terminal through the electric starter and back to the positive terminal. This is a DC circuit and electrons migrate through the circuit from negative to positive terminal. About how long must the key be in the ON position for electrons starting from the negative terminal to reach the positive terminal?
A time shorter than the human reflex turning a switch on or off
B. ¼ second
C. 4 seconds
D. 4 minutes
E. 4 hours
Answer: about 4 hours

3. Why does the light come on at once if vd is so small?
Without electric field
With electric field
Why does the light come on at once if vd is so small?

4. 24.1 Current, drift velocity and current density

5. 0.28 mm/s - but they all start moving at once

6. 24.2 Conductivity and Resistivity
The presence of electric fields in conductors results in electric current
No longer have electrostatic equilibrium
Collisions oppose the electric force, and the electric field sustains a steady current

7. Answer: No
No voltage difference across its body, no current flows

8. 24.3 Resistance and Ohm’s Law

9. defines R for any conductor

11. Now will the bird get…. ?

13. 24.4 Electric Power

14. Answer: D
It consumes the most energy per second (power)

15. Answers: B An electric motor consumes energy, not electricity.
A generator generates electric energy