How to find e/m and % error calculation for the following data that was recorded? 

Results and Calculations Diameter (inside to inside of coils): 32cm Radius: 16cm= 0.16m AV = 250 V Trial Voltage (V) Current (A) Radius (cm) Magnetic Field (T) 1 250 2.58 2.5 -3 1.88 10 2 250 2.46 2.75 -3 1.80 10 3 250 2.24 3 -3 1.64 10 4 250 2.08 3.25 -3 1.52 10 5 250 1.94 3.5 -3 1.42 10 9 250 1.82 3.75 1.33 x 10-3 7 250 1.70 4 -3 1.24 10 8 250 1.62 4.25 -3 1.18 10 9 250 1.52 4.5 1.11 10- 10 250 1.42 4.75 1.04 10 3 -3