unit8 ohm27s law.ppt

1、Ohms law,在同一電路中，導(dǎo)體中的電流跟導(dǎo)體兩端的電壓成正比，跟導(dǎo)體的電阻成反比,這就是歐姆定律 .,歐姆定律公式：I=U/R,Fast reading,Answer the following questions according to the text. 1.Who was Ohm? 2.What contribution did Ohm make in physics? 3.Can you tell Ohms Law in English? 4.What is potential difference? 5.How do you calculate voltage in a ci

2、rcuit? 6. How do you calculate resistance in a circuit?,Careful reading,Paragraph 1,Georg Simon Ohm(1787-1854),A German physicist,Electrical currents,The unit of electrical resistance,Formulation of the relationship between current ,electromotive force and resistance,paragraph2,Electric circuit,A co

3、ntinuous path,Conductors,Conducting devices,A source of power,Not continuous,(a closed circuit),(an open circuit),Paragraph 3,4,The current flowing through a resistor is directly proportional to the potential difference across its ends providing the temperature remains constant.,R=V/I (resistance =v

4、oltage/current),The conductor between the two locations,The potential difference,The amount of current,(DC,AC),Example,If a current of 2 amperes flows through the circuit which has a resistor of 10 ohms ,and the resistance of the wire used in the circuit is 6 ohms, calculate the voltage or the potential difference across the circuit.,R=R1+R2=10 +6 =16 V=I