I will love you forever if you help me with these two questions ****
1) An automobile starter is connected to a 12-volt battery. If the starter has an effective resistance of 2.5 ohms, what is the rate at which electrons drift past a point in the circuit?
2) A certain material is formed into a long rod with a square cross section 0.50cm on each side. When a voltage of 100V is applied across a length of a rod 2.0m long, 5.0A of current is carried. What are (a) the resistivity and (b) the conductivity of the material? (c) is it a conductor, insulator, or semiconductor?

Question

I will love you forever if you help me with these two questions ****
1) An automobile starter is connected to a 12-volt battery. If the starter has an effective resistance of 2.5 ohms, what is the rate at which electrons drift past a point in the circuit?
2) A certain material is formed into a long rod with a square cross section 0.50cm on each side. When a voltage of 100V is applied across a length of a rod 2.0m long, 5.0A of current is carried. What are (a) the resistivity and (b) the conductivity of the material? (c) is it a conductor, insulator, or semiconductor?

anonymous · Answer

** for 2, I got the answers of  20 ohms for a, 4000 for b and semiconductor for c, but I just want to make sure that I got it right!~ #1 I have no idea :(

anonymous · Answer

First one is simply i=V/R. V=12v and R=2.5 ohms. 
Second one, (a) resistivity is not just resistance. it is the specific resistance. |dw:1392781237343:dw|
Find resistivity using the values of R, length and area with the above formula.Here, area of cross section= area of a square using the given side. Do remember to conver the 0.5 cm to meters as ur length is given in meters. Or you can convert your length to cm. R can be found using R=V\i. 
Conductivity = 1/resistivity. 
If your answer is too small, then it an insulator. If it is large, it is a conductor. Intermediate value indicates that it is a semiconductor.