Chapter 21 potential 第八章静电场 ◆电势零点选择方法:有限带电体以无穷远为电势零点, 实际问题中常选择地球电势为零. Choose the potential to be zero at an infinite distance or the ground. E·dZ ◆物理意义把单位正试验电荷从点A移到无穷远 时,静电场力所作的功 Descriptions: y is a property of an electric field, regardless of whether a charged object has been placed in that field; U is an energy associated with a system(the charged object plus the charged particles that set up the electric field)
Chapter 21 potential 第八章静电场 电势零点选择方法：有限带电体以无穷远为电势零点， 实际问题中常选择地球电势为零. Choose the potential to be zero at an infinite distance or the ground. A A V E l d 物理意义 把单位正试验电荷从点 移到无穷远 时，静电场力所作的功. A Descriptions: V is a property of an electric field, regardless of whether a charged object has been placed in that field; U is an energy associated with a system (the charged object plus the charged particles that set up the electric field)
Chapter 21 potential 第八章静电场 4 Electric potential Difference(p503电势差,电压): The av between any two points a and b equal to in magnitude work done by the fe on unit positive charge during the move from a to 6. △V=V-V=E·dl C Ed=Edi ◆△ is independent on the choice of reference potential(电势的零点无论选在何处电势差不受影响) A The value of electric potential is relative, but the one of electric potential difference is absolute.(电势的大小是相对的,电势差是绝对的)
Chapter 21 potential 第八章静电场 4 Electric Potential Difference (p503电势差,电压): b a b a a b V V V E l E l E l d d d The V between any two points a and b equal to in magnitude work done by the on unit positive charge during the move from a to b. Fe The value of electric potential is relative, but the one of electric potential difference is absolute. (电势的大小是相对的,电势差是绝对的) V is independent on the choice of reference potential (电势的零点无论选在何处电势差不受影响)
Chapter 21 potential 第八章静电场 o A convenient way of calculating work done to move a charged particle g through a potential difference△ from a to b(电场力所做功的计算方 法): Wa =q(-Vh In any situation, charged particle moves under fe its potential energy U always tends to decreasing. Thus a positively charged object moves naturally from a high potential to a low potential. A negative charge does the reverse
Chapter 21 potential 第八章静电场 ( ) Wab q Va Vb A convenient way of calculating work done to move a charged particle q through a potential difference V from a to b (电场力所做功的计算方 法): In any situation, charged particle moves under , its potential energy U always tends to decreasing. Thus a positively charged object moves naturally from a high potential to a low potential. A negative charge does the reverse. Fe
Chapter 21 potential 第八章静电场 21-2 &21-3 &21-4 Calculation of electric Potential (P505-511) △=V-V=Ed-E·d=E·dl A E·dl A∞o
Chapter 21 potential 第八章静电场 21-2 & 21-3 & 21-4 Calculation of Electric Potential (P505-511) A A V E l d b a b a a b V V V E l E l E l d d d
Chapter 21 potential 第八章静电场 I. Potential Due to a Point Charge(p507-508) e= q 令V=0 4 ar E q 4丌enr q q r4兀Enr 2 4t er >0 produces a positive electric potential; 9<0, produces a negative electric potential
Chapter 21 potential 第八章静电场 q>0 produces a positive electric potential; q<0, produces a negative electric potential. q r l d E dr r r q E ˆ 4 π 2 0 1. Potential Due to a Point Charge (P507-508) 令 0 V r r l r q V ˆ d 4 π 2 0 r r q r 2 π 0 4 d r q V π 0 4