निम्नलिखित में से कौन सा विद्युत उपकरण अपने प्राथमिक कार्य सिद्धांत में 'विद्युत धारा के चुंबकीय प्रभाव' का उपयोग नहीं करता है?

How does the magnetic field at a distance r from an infinitely long wire change if the current is doubled?

The force on a current-carrying conductor in a magnetic field is maximum when _____.

An electron moves vertically downwards into a magnetic field directed towards the right. According to Fleming's Left-Hand Rule, the direction of the magnetic force acting on the electron will be: