A bidirectional meter for a consumer with rooftop generation must
Answer: A
Import and export are usually valued differently, so the two must be accumulated separately rather than netted by a single register. A static meter does this by detecting the sign of the power and directing the accumulated energy to the appropriate register.
Please log in or register to report this question.
The quantity that fixes how many gear teeth are needed between the spindle and the register of a meter is
Answer: B
The register must advance by one kilowatt hour for every K revolutions of the disc, so the gear ratio follows directly from the constant. A meter of a different constant needs a different train, which is why the constant is stamped on the nameplate.
Please log in or register to report this question.
Two identical energy meters are connected in series in the same circuit. Over an hour they will
Answer: C
Their current coils carry the same current and their pressure coils see nearly the same voltage, so each measures the same power and registers the same energy. The tiny drop across the first coil makes an immaterial difference, and this is a standard way of comparing two meters.
Please log in or register to report this question.
The reason a shunt magnet is highly inductive while a wattmeter's pressure coil is deliberately made nearly resistive is that
Answer: D
The wattmeter multiplies two currents directly, so its pressure coil current must be in phase with the voltage. The meter multiplies two fluxes through a sine, so it needs one of them in quadrature with the voltage. The requirements are opposite for the same reason: to obtain the cosine.
Please log in or register to report this question.
