124 APPLY AND ANALYZE 1. What are six basic sources of electricity or electromotive force? 2. What is polarization? 3. What are some benefi ts of using a mercury cell? 4. What determines the capacity of a storage battery? CRITICAL THINKING 1. Discuss the advantages and disadvantages of a solar powered boat. 2. Explain how a hydrometer operates and how it is used to test electrolyte of a rechargeable battery. 3. What could be done to save electrical energy at your school? 4. Explain why gel and AGM battery designs are used in specifi c applications, such as airplanes. Copyright Goodheart-Willcox Co., Inc.