When the voltage at both ends of a conductor is 3 V, the current passing through it is 200 ma. What is the resistance of the conductor Now increase the voltage to 5 v. if there are two kinds of ammeters with 0-0.6 A and 0-0.3 a ranges, which range should be chosen to measure the current of conductor?

When the voltage at both ends of a conductor is 3 V, the current passing through it is 200 ma. What is the resistance of the conductor Now increase the voltage to 5 v. if there are two kinds of ammeters with 0-0.6 A and 0-0.3 a ranges, which range should be chosen to measure the current of conductor?

R = u / I = 3V / 0.2A = 15 Ω
I = u / r = 5V / 15 Ω = 0.3A
Choose 0-0.6 a, because this is not too accurate, it may exceed the range, so choose the larger one

How many kilowatts use how many a circuit breaker to calculate?

Single phase 8a, three-phase 2a, times kW = rated current of circuit breaker

How many a switches does an 8 kW appliance need
What kind of switches and wires do 8 kW electrical appliances need?

8000W/220V=36.36A
Need at least
40mm copper wire for 40A air brake

Three, 380 V, 400 a equivalent to how many kilowatts of available electricity ah, how to calculate

1.732×0.38KV×400A=263kva
Generally, the power factor is 0.8, and the power is 210Kw
That is to say, the pure resistance of this power supply can use 263kw,
Nonlinear load, can use 210Kw