英文物理题(circuit)Inthecircuitshown,itmakesnodifferencewhethertheswitchisopenorclosed.Whatisemfε3intermsoftheotherquantitiesshown?Thecircuitdiagramishere:

Question

英文物理题(circuit)
In the circuit shown,it makes no difference whether the switch
is open or closed.What is emf ε3 in terms of the other
quantities shown?
The circuit diagram is here:

Answer 1

it makes no difference whether the switch
is open or closed,表明ε3等于开关打开时ε1ε2结点以及R1R2结点两端电压.求出这个电压就行.
还是用原始的方法吧,电流I=(ε1+ε2)/(R1+R2)
电压ε3=ε2-R2*(ε1+ε2)/(R1+R2)=(ε2*R1-ε1*R2)/(R1+R2)