Question

What is the magnitude of δv12 if the bulb is removed from the socket (i.e. the circuit is not closed)?

Answer 1

If the socket is open after removing the bulb, then the substitute value is
I = 0 A
ΔV₁₂ = IR
= (OA)(2Ω)
= 0 V

Answer 2

Since the circuit is incomplete or not closed, no current flows in the circuit. as per ohm's law , Voltage is directly proportional to current and is given as

V = Voltage = i R where i = current , R = resistance

as no current flows in the circuit, i = 0

the resistance R can not be zero. hence

V = 0 (R)

V = 0 Volts

so the magnitude of the Voltage is zero Volts