电学基础（Electrical basis）.docVIP

电学基础（Electrical basis） Current particlepreparation charge t- time I current IKA = 1000A Voltage (potential, current) Uab = Wab/Q, Wab- Joule, J, Q - charge Coulomb C Uab voltage volts 1KV = 1000V V Voltage reference point - power a point The voltage between two points is called voltage drop The current -- one from one current to another The resistance R resistance (ohms) - resistivity The length L (m) s cross-sectional area (mm2) Choice item: reduce the cross section of a certain length to half its resistance is 4 times that of the original. Ohms law formula conversion U = IR The resistance is directly proportional to the voltage across the power supply; Ohm law of all circuit R0 loop resistance (resistance, power circuit resistance) I is the current circuit, R+R0 is the entire circuit resistance. Whats the Ohms law of the whole circuit, Jane? (D) Answer questions 1, known: E = 6V, R = 2.9, I = 2A, Seek 1, R0 =? 2, when R = 5.9, I =? According to Ohm law of whole circuit : 1, RR0 = V/I = (6/2=3-2.9=0.1) 2, when R is 5.9: = 6/5.9+0.1=1 Answer: R0=0.1; I=1A Kiel current Hof law According to the diagram: I3 = -2.5A, I4 = 1A Kiel voltage, Hofs law, U1 + U2 = U3 = U4 = 0 In any closed loop, all voltage sets are equal to zero Resistance series circuit a number of resistance terminals are connected in turn, so that the current is only one way of connection, called resistance series. Series circuits have the following characteristics: 1 、 each resistor in the circuit flows through the same current. That is, I = I1 = I2 = I3. 2 、 the sum of the voltage drops on each resistor is equal to the total voltage, U = IR1+IR2+IR3 = U1+U2+U3. 3, the total resistance is equal to the sum of each resistor, that is, the total resistance = = R1+R2+R3 4, the ratio of the voltage drop on each resistor is equal to its resistance ratio U1/U2=R1/R2 U1/U3=R1/R2 (partial pressure formula). Equivalent to Example: in figure (a), if U = 140V, I = 4A, R1 = 10 (), R2 = 15 (), R3 and U3. Solution = = U