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No. You cannot rule out the battery even after the open circuit voltage measurement. The open-circuit voltage may not have changed but the battery's internal resistance may have greatly increased.
Answer:
The maximum potential difference is 186.02 x 10¹⁵ V
Explanation:
formula for calculating maximum potential difference

where;
Ke is coulomb's constant = 8.99 x 10⁹ Nm²/c²
k is the dielectric constant = 2.3
b is the outer radius of the conductor = 3 mm
a is the inner radius of the conductor = 0.8 mm
λ is the linear charge density = 18 x 10⁶ V/m
Substitute in these values in the above equation;

Therefore, the maximum potential difference this cable can withstand is 186.02 x 10¹⁵ V
For electrical devices . . .
Power dissipated = (voltage) x (current) =
(12 V) x (3.0 A) = 36 watts .
1 watt means 1 joule per second
(36 joule/sec) x (60 sec/min) x (10 min) = 21,600 joules