How many default No of Partition


I am attending interviews, but i stuck with the fallowing questions. Please reply if you anybody know answers.

  1. How many partitions does Spark default create for a large data files ?
  2. If spark creates default number of partitions of 5, why we need to use coalesce and repartion to increase the number of partition.
  3. Suppose i have 4 partitions with 1 GB of parition, and in spark-submit i given 5 executor core with 4GB of exeutor memory , how spark will perform the task?

Please reply if know the answer

Thanks and Regads