12. The work done would be equal to QΔV, so W = (5.0 C)(1.5 V) = 7.5 J.
13. The potential difference applied to the metal plates can be calculated using the formula ΔV = Ed, where E is the electric field strength and d is the distance between the plates. So, ΔV = (2.50 x 10^3 N/C)(0.500 m) = 1250 V.
14. Option (d) None of the above is correct for an ohmic material.
15. The magnitude of the electric field between the plates can be found using the formula E = V/d, where V is the potential difference and d is the distance between the plates. Therefore, E = 60.0 V / 0.030 m = 2000 V/m or 2.0 x 10^3 N/C.
16. The potential drop across a wire is directly proportional to the current flowing through it, according to Ohm's Law (V = IR).
17. The equivalent resistance of resistors in parallel can be calculated using the formula 1/Req = 1/R1 + 1/R2 + 1/R3. Therefore, 1/Req = 1/70 + 1/90 + 1/120 = (36/630) + (35/630) + (28/630) = 99/630. Therefore, Req = 630 / 99 = 6.36 ohms. The total current supplied to the circuit is given as I, so the potential drop across the resistors R1 and R2 can be calculated using Ohm's Law (V = IR). V1 = (70)(I) and V2 = (90)(I).