unit8 ohm27s law（課堂PPT）

1、1Ohms law2在同一電路中，導體中的電流跟導在同一電路中，導體中的電流跟導體兩端的電壓成正比，跟導體的電體兩端的電壓成正比，跟導體的電阻成反比阻成反比,這就是歐姆定律這就是歐姆定律 . 歐姆定律公式：I=U/R 3Fast 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?

2、5.How do you calculate voltage in a circuit?6. How do you calculate resistance in a circuit?4Careful readingParagraph 1Georg Simon Ohm(1787-1854)A German physicistElectrical currentsThe unit of electrical resistanceFormulation of the relationship between current ,electromotive force and resistance5p

3、aragraph2Electric circuitA continuous path Conductors Conducting devicesA source of power Not continuous(a closed circuit)(an open circuit)6Paragraph 3,4 The current flowing through a resistor is directly proportional to the potential difference across its ends providing the temperature remains cons

4、tant.7R=V/I (resistance =voltage/current)The conductor between the two locationsThe potential differenceThe amount of current(DC,AC)8Example 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.9 R=R1+R2=10 +6