144 4 damentals Industri I d d s ia l l Rob o bo tics s Fu un Copyright Goodheart-Willcox Co., Inc. Copyright Goodheart-Willcox Co., Inc. Activity 6-2 Basic Electrical Problem Solving Objectives Basic electrical problems are often encountered in any area which involves electrical control systems. Robotics is no exception. The most basic problems in electrical systems involve Ohm’s law. Ohm’s law is a mathematical formula which explains the relationship between voltage, current, and resistance. This relationship must be understood before electrical concepts are meaningful. In this activity, you will b complete some practical problems by applying Ohm’s law. Analysis 1. A doorbell requires 0.2 ampere of current in order to ring. The voltage supplied to the bell is 120 volts. What is its resistance? 2. A relay used to control a motor is rated at 25 ohms resistance. What voltage is required to operate the relay if it draws a current of 0.25 ampere? 3. An automobile battery supplies a current of 7.5 amperes to a headlamp with a resistance of 0.84 ohm. What is the voltage delivered by the battery? 4. What voltage is needed to light a lamp if the current required is 2 amperes and the resistance of the lamp is 50 ohms? 5. If the resistance of a radio receiver circuit is 240 ohms and it draws a current of 0.6 ampere, what voltage is needed? V I R Goodheart-Willcox Publisher Ohm’s law circle: V, voltage V V I, current R, resistance. To use the circle, cover the value you want to fi nd and read the other values as they appear in the formula: fi V = I × R, × I = V/R, R = V/I.