The derivation process is as follows:
1, P=UI is known, the voltage-current relationship is U=IR, and the combination results in P = I 2r. Mainly suitable for pure resistance circuits. It is usually used in series circuits or to solve electric power when current and resistance change.
2. It is known that P=UI, the relationship between voltage and current is U=IR, and the combination results in p = u 2/r.. Mainly suitable for pure resistance circuits. Generally speaking, it is used for parallel circuits or when there is a voltage and resistance variable to solve the power.
3. In the case of pure resistance (all electric energy is converted into internal energy "heat energy"), electric heating is completely equal to electric work. The formula derived from Joule's law formula: Q = I 2RT is: Q = W = Pt = UIT = I 2RT = U2t/R.
Extended data
Different formulas have different scope of application. Other commonly used formulas related to electric power are as follows:
1, W=UIt (empirical value, applicable to any circuit)
2、W=Q？ (empirical, only applicable to pure resistance circuits. Where w is the work done by the current flowing through the conductor and q is the heat generated by the current flowing through the conductor)
3. w = I 2rt (compound formula, only applicable to pure resistance circuits)
4, w = u 2t/r (compound formula, only applicable to pure resistance circuits)
5. p1:p2 = u1:U2 = r1:R2 (the relationship between electric power and voltage and resistance in series circuit: in series circuit, the ratio of electric power is equal to the ratio of their corresponding voltage and resistance).
6. p1:p2 = I1:I2 = R2: r1(the relationship between electric power and current and resistance in parallel circuit: in parallel circuit, the ratio of electric power is equal to the ratio of their corresponding current and the inverse ratio of their corresponding resistance).
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