Seven
Formula
I'm assuming that the formula used is
R = R_ref [1 + α*(T - T_ref)=
Givens
- R_ref is the starting resistance of 100 ohms
- α (alpha) = 4.0 *10^-4 or 0.00040
- T_ref = 11.5 degrees Celcius
- T = 10 degrees.
- R=??
Solution
R = 100[ 1 + 4.0*10^4(10 - 11.5)] Collapse the brackets.
R = 100[ 1 + 4.0*10^4(-1.5)] Simplify
R = 100[1 - 0.00060] Subtract
R = 100[0.9994] Multiply
R = 99.94
Answer: A
Eight
The accepted formula for resistance and resistivity is
R = ρ * A / L where
rho is the resistivity
A is the face Area of the conductor
L is the length of the conductor.
Now a perfect conductor has a resistance of 0.
So since resistivity is a direct variation with resistance, its value also has to be 0.
Answer: A
Nine
The formula you need for this is W = I^2* R
W = 14 Watts
R = 17 ohms
I = ??
14 = I^2 * 17 Divide bother sides by 17
14/17 = I^2
0.8235 = I^2 Switch and take the square root of both sides.
I = sqrt(0.8234)
I = 0.9075 Answer: D