Why do you sometimes use UI for power and I2R for power?

Updated on number 2024-02-09
8 answers
  1. Anonymous users2024-02-05

    UI calculates the total power consumption, while i2R calculates the heat generation, but they are equal in pure resistive circuits (i.e., only resistors or lamps and the like) and different in non-pure resistive circuits. For example, in a circuit with an electric motor, the total electrical power consumed during UI, and I2R is the power consumed by heat generation in the circuit, and according to the conservation of energy, UI-I2R is the remaining power converted into mechanical energy.

  2. Anonymous users2024-02-04

    The UI is available for all circuits.

    Whereas, i r is only applicable to pure resistance circuits, that is, the work done by the current is only converted into internal energy, not into other forms of energy such as mechanical energy.

    If you calculate the power of an electric motor, you can't use ir, because the electric motor converts most of the electrical energy into mechanical energy.

  3. Anonymous users2024-02-03

    p=ui...Definition, which is generally applicable when calculating electrical power.

    In a purely resistive circuit, p=ui=uuu=iir is true.

    When connecting in series, it is more convenient to use p=iir.

    When parallel connection, it is more convenient to wait for u, and it is more convenient to use p=uu r.

    In impure resistive circuits:

    Electrical power consumed p = ui, thermal power = iir

    For example, the electric energy consumed per unit of motor = ui, the heat energy generated per unit time = iir, and the mechanical energy obtained per unit time = ui-iir

  4. Anonymous users2024-02-02

    Looking at the known conditions, it is actually the same.

    Because P=UI=IR*I=I2R, it's actually the same, but UI is more versatile, not all circuits are resistive, and there are also capacitors and inductors, at that time, I2R may not be applicable.

  5. Anonymous users2024-02-01

    p=ui is a definitive formula that can be used in any circuit, while the last two are extrapolated from Ohm's law and are only applicable to purely resistive circuits, i.e. electronic components where electrical energy can only be used to produce thermal effects.

  6. Anonymous users2024-01-31

    Electrical power p = ui = i r = u r

    Note when applying:

    1.In this set of formulas, there is usually an invariant resistance r, but the voltage u and current i are often variable;

    2.In most practical cases, the voltage is also constant, such as 220V, at this time there is only the current i position, but given such as electric furnace, light bulb, etc., the rated power is determined p = u r;

    3.Correspondingly, if both the rated power and the rated voltage tell you, the resistance r is determined, which is the key r = u p;

    4.Sometimes the voltage fluctuates, not the rated voltage such as 220V, as long as you know that the resistance r is the result of the above method calculation, you can get the new current i = u r with the new voltage and resistance, so that the new power will also know p new = u new r = i new r;

    5.There is no better than this for regular questions; Regardless of three, seven, twenty-one, seeking r first is the key.

  7. Anonymous users2024-01-30

    (1) p=ui is universal, (2) p=i2r and (3) p=u2r

    It is only applicable to the circuit that converts all the electrical energy into internal energy, and the formulas can be applied to both the series circuit and the parallel circuit, so the ACD is wrong, and B is correct;

    Therefore, choose B

  8. Anonymous users2024-01-29

    Here u is the delivery voltage, not the voltage assigned to the delivery circuit. u includes the voltage allocated to the transmission circuit (a small part) and the voltage allocated to the electrical appliance (a large part).Therefore, it is not possible to calculate the electrical power consumed by the delivery circuit with the PUI.

    For example, if the transmission voltage is 220V, but in this 220V, the voltage of 10-20V will be distributed to the transmission line, and the voltage of about 200V will be distributed to the electrical appliances, so you can not use the voltage of 220V to calculate the power consumed by the transmission line, but can only use the voltage of 10-20V. But with p i 2 r it is okay because i is the current through the transmission line and r is the resistance of the transmission line.

    Got it clear!

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