Questions

Multiple-choice questions you can practise one by one. Open a question, tap an answer and see at once whether it is right. For a random set, try Quick practice.

941 questions

• What is the main purpose of a freewheeling diode in an RL-load controlled rectifier?

  Industrial Electronics & Control of Drives › Unit 2: Controlled Rectifiers · Medium

• A chopper is a power-electronic converter that converts:

  Industrial Electronics & Control of Drives › Unit 3: Inverters, Choppers, Dual Converters and Cyclo-Convertors · Easy

• In an SCR, the three terminals are called:

  Industrial Electronics & Control of Drives › Unit 1: Introduction to Thyristors · Easy

• When selecting an insulating material for a high-voltage component, why is dielectric strength alone insufficient?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why may dry wood provide useful insulation in one installation but be unsuitable in another?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why is the thermal class of enamelled winding wire important when selecting it for a motor?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• What is the principal difference between coating varnish and impregnation varnish in electrical windings?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why should silicone grease be applied only where its formulation is suitable for the electrical interface?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why is the dielectric loss tangent of an insulating material important in high-frequency applications?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Which combination best explains the use of PTFE in demanding electrical insulation applications?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why should bitumen-based insulation be selected with care for an application involving substantial temperature variation?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• A flexible cable is installed near oil and elevated temperatures. What should guide the choice of rubber insulation?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why must natural insulating fibres such as silk and jute be evaluated for moisture absorption and ageing?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why can voids within a solid-paper insulation system be particularly dangerous under high electric stress?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why is impregnated paper widely useful in certain high-voltage insulation systems?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why is untreated cotton generally less dependable than properly treated insulation in humid electrical service?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• An insulating material must withstand repeated thermal cycling and mechanical stress. Why should glass selection include mechanical design considerations despite its high electric…

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why is steatite used for certain high-temperature insulating supports?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why may a porcelain insulator fail electrically even when the bulk ceramic has high resistivity?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard

• Why must asbestos-containing insulating materials be treated as a health hazard during maintenance or removal?

  Electrical Engineering Materials › Unit 3: Insulating Materials · Hard