Most mechanical reasoning and electrical reasoning tests introduce basic concepts of Newtonian mechanics and static and dynamic electricity. The focus is usually not on calculations, but understanding of the basic principles involved. The questions are usually standard multiple-choice questions, where only one answer is correct out of several optional answers. As the tests are timed, rehearsing the concepts and knowing what questions usually look like improves performance in terms of both accuracy and response time.
Note that if you are applying to a position that requires more vocational experience, you may be requested to take a Ramsay Mechanical Test. Based on your position, that may be the Ramsay Electrical Maintenance Test for electrical jobs, the Ramsay Maintenance Test for maintenance jobs, or the Amazon Tech Test, if your position is part of an outsourcing service for Amazon.