单项选择题 A direct current passing through a wire coiled around a soft iron core is the description of a simple（）.

单项选择题 Which of the following electric motors would be the safest and most reliable to use on the main deck of a vessel in foul weather conditions?（）

单项选择题 A resistance in a circuit of unknown value is to be tested using the voltmeter/ammeter methodTherefore, the meters should be connected with（）.