There is a step up transformer that doubles the voltage if the primary voltage of 10 v what will the voltage in the secondary coil be

20volts

Explanation: in a step transformer, the voltage on the secondary coil is usually lower than that of the primary coil and in this case, the question says if it’s doubled, therefore the voltage at the primary side will be doubled or Multiplied by 2:

Therefore Vs = 2Vp

Therefore Vs = 2 x 10v = 20volts

where is the circuit diagram ?

this could be newton#'s law of cooling. the cooling curve is exponential