Fill in the blank in the given nuclear reaction. 

____ + 

8. To convert a pure semiconductor into n-type semiconductor, what type of impurity is added to it?

Choose the correct alternative (a), (b), (c) or (d):

• ∈₀= 9∈_w 

• ∈₀=81∈_w

• ∈_w=9∈₀ 

• ∈_w=81∈_o 

Five resistors are connected as shown in Figure 



The effective resistance i.e. equivalent resistance between the points A and B is:

• 4Ω 

• 5Ω

• 20Ω   

• 20Ω