Open circuit Voltage occursa.At zero currentb.when the circuit is short-circuitedc.when resistance is zero

Open circuit voltage occurs at zero current. This is because an open circuit doesn't allow current to flow. In an open circuit, the path through which electricity would flow is disconnected. Therefore, there is no current because there is no path for it to flow. However, the voltage doesn't disappear because it's the cause of the current, not the result. So, even if there's no current, there can still be voltage. This is known as open circuit voltage.

It does not occur when the circuit is short-circuited or when resistance is zero. In a short circuit, the resistance is nearly zero, causing the current to be very high. This is the opposite condition of an open circuit. When resistance is zero, it's a condition of a superconductor, not an open circuit. In a superconductor, current can flow without any resistance, which is also the opposite of an open circuit where no current can flow.