ELECTRICAL CIRCUITS

There are two types of electrical circuit arrangements.
1. Parallel circuits: There is an alternate path to the flow of the current if other paths are blocked.

Note on diagram below: The symbol "R" represents any form of resistance such as bulb resistors, etc. The symbol "E" represents a cell such as battery, a current generator.

2. Series circuit: There is only one path for the current to flow. When this path is blocked, there will be no flow of current.
 
 Animation in a series circuit.

UNITS OF ELECTRICAL QUANTITIES

Variable	Symbol	Unit	Symbol
Voltage	V	Volts	V
Current	I	Ampere	A
Resistance Power	R P	Ohm Watt	Ω W

Formulas you should know:

1. Voltage = Current x Resistance

2. Power = Voltage x Current

You should be able to use these formulas in calculations.

NUTRITIONAL FACTS PROBLEMS

Nutrition Facts  
Serving size 100 grams
Amount per serving
Calories?  
                                      % Daily Value
Total Fat 22 g               33%
Saturated Fat 10 g          50%

Cholesterol 80 mg         26%
Sodium 54 mg               2%

Carbohydrates 0 g         0%
Dietary Fiber 0 g           0%
Sugars 0 g

Protein 24 g                  48%

QUESTIONS:

1. Estimate the number of Calories per serving from the above food label.

A. 194 cal

B. 160 cal

C. 294 cal

D. 400 cal

2. Which of the following foods is the most likely source of this label?

A. strawberry

B. Butter

C. Steak

D. Oatmeal

ANSWERS:

1. C  (Use the fact that carbohydrate generates 4 cal/gram; fat 9 cal/gram; and proteins 4 cal/gram)

2. C

QUESTIONS FOR THE DAY

1. A child who is 7 years old, lifts a 40 kg-bag from the floor onto a table that is 3-feet high from the floor. If an adult, who is 25 years old lifts the same bag from the floor onto the same table, who do you think has done more work?

A. The child

B. The adult

C. Both did the same amount of work

D. No work is done

2. A child who is 7 years old, lifts a 40 kg-bag from the floor onto a table that is 3-feet high from the floor. If an adult, who is 25 years old lifts the same bag from the floor onto the same table, who do you think put in more energy?

A. The child

B. The adult

C. Both did the same amount of work

D. No work is done

ANSWERS

Work is defined as the force times the distance through which it acts.

Work = Force x Distance

1. C The force is derived from the mass of the bag which is its weight. Remember F = mg. That is, Force = mass x acceleration due to gravity. Since they lift the same weight through the same distance of 3 feet onto the table, the work done by both of them is the same.  

2. A The work done is the same but the child puts in more energy to do the same amount of work. Energy is the ability to do work.

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