1. [Show][Hide]
   1. 
   Explanation: No current flows so pd across r = 0V
   Pd from P to S = 12V
   
   
2. [Show][Hide]
   4. 
   Explanation: Total resistance = V/I = 12/0.5 = 24Ω
   Internal resiatnce = 4Ω
   
   
3. [Show][Hide]
   3. 
   Explanation: Total EMF = 6-6+6 = 6V
   I=V/R = 6/6= 1 A
   
   
4. [Show][Hide]
   1. 
   Explanation: Total EMF = 12+12 +6 = 30V
   I=V/R = 30/12 = 2.5 A
    
   
   
5. [Show][Hide]
   4. 
   Explanation: The one in the middle draws no current so can be ignored.
   Two 12Ω in series = 24Ω
   two 24Ω in parallel = 12Ω
   
   
6. [Show][Hide]
   1. 
   Explanation: R = 12 + 6
   
   
7. [Show][Hide]
   2. 
   Explanation: Two 12's in parallel = 6Ω
   Total = 6 + 12 = 18Ω
   
   
8. [Show][Hide]
   1. 
   Explanation: Total of each combination of 12 and 6 = 4Ω as in qu.1

   Two 4Ω in parallel gives 2Ω
   
   

9. [Show][Hide]
   3. 
   Explanation: 1/R = 1/12 + 1/12 + 1/6 = (1 + 1 + 2)/12 = 4/12
   R = 12/4
   
   
10. [Show][Hide]
    2. 
    Explanation: 1/R = 1/R₁ + 1/R₂ = 1/6 + 1/12 = (2+1)/12 = 3/12
    R = 12/3
    
    

All answers: [Show] [Hide]