2. Formula: (I=U/R), where the unit is: i→ an (a); U→ volt (v); r→ω(ω)。 1 A = 1 V/O。
3. Understanding of the formula: ① I, U and R in the formula must be in the same circuit; ② If any two of I, U and R are known, the other quantity can be found; (3) Units should be unified when calculating.
4. The application of ohm's law:
(1) The same resistor has the same resistance regardless of current and voltage, but when the voltage across the resistor increases, the current passing through it also increases. (R=U/I) ② When the voltage is constant, the greater the resistance, the smaller the current will be. (I=U/R)
(3) when the current is constant, the greater the resistance, the greater the voltage across the resistance. (U=IR)
5. The series connection of resistors has the following characteristics: (refer to R 1, R2 series connection) ① Current: I=I 1=I2 (the currents in all parts of the series circuit are equal) ② Voltage: U=U 1+U2 (the total voltage is equal to the sum of the voltages in all parts) ③ Resistance: R = R65438+.
N resistors with the same resistance are connected in series, so there is R total =nR.
④ partial pressure
⑤ Proportional relation: current: I1:I2 =1:1.
6. Resistance parallel connection has the following characteristics: (refer to R 1, R2 parallel connection) ① Current: I=I 1+I2 (main current is equal to the sum of the currents of each branch) ② Voltage: U=U 1=U2 (main voltage is equal to the voltage of each branch) ③ Resistance: (The reciprocal of the total resistance is equal to the parallel resistance.
And) if n resistors with the same resistance are connected in parallel, there is1/r.
Total =1/r1+1/R2.
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④ Shunt function: I1:I2 =1/r1:1R2.
⑤ Proportional relation: voltage: u1:U2 =1:1.