AUTOTECH Kerala

WORK : Work is said to be done by force F when the point of its application moves Mathematically, through a distance S. Work = force x distance            = F x S an acceleration of one The unit force in the mks system is newton (N). defined as the force acting on one kilogram mass of a body for one second which gives metre per second. If in the above equation, . force = 1 N and distance = 1 m, then Work done = 1 N-m or joule (J) In the mks system of units, work done is given in joules. It is defined as the work done by a force of one newton when the point of its application moves through a distance of one metre in the direction of the force. Therefore 1 J = 1 N-m POWER :  Power may be defined as the rate of doing work. Mathematically, work done Power time Note : Work done or energy expanded = power x time. If in time t sec, a quantity of electricity Q is transferred between the ends of a conductor when a potential difference is V, then  Work done per second = VQ/t But. Q

AMMETER An ammeter is required to measure the current. Therefore, it must be connected in series to the load of which the current is to be measured. As it is connected in series, it must have low resistance, otherwise the resistance of the instrument will appreciably change the current through the load. For connecting it in series with the load, open the circuit at one place and connect the meter in the circuit as shown in Figure. Note : An ammeter should never be connected in parallel with the load otherwise it can get damaged. VOLTMETER A voltmeter is used to measure the potential difference. Therefore it must be connected in parallel to the circuit of which the potential difference is to be measured. A voltmeter must have high resistance otherwise it will take heavy current. When a voltmeter is connected in series, it measures the voltage drop across its own terminals. For connecting the voltmeter in parallel to the circuit, the meter should be connected across the load

CONNECTING ELECTRICAL CIRCUITS When electrical components are connected, they may be placed either end on end (called series circuit) or side by side (called parallel circuit). SERIES CIRCUITS : When circuit components are connected with only one conducting path they are said to be connected in series. The same current is in all components. When batteries are connected in series, (the voltage obtained in the circuit will be a total of the voltage in the batteries. This principle is used in car batteries and many radio batteries, where voltages larger than 1.5 or 2 volts are required. In these cases the cells are joined together in series. If resistors are connected in series the resistance in the circuit will be equal to the sum of all resistors. i.e.  R = R1 + R2 + R3 + R4 PARALLEL CIRCUITS : When circuit components are connected with several conducting paths between the sources of e.m.f. they are said to be connected in parallel. When batteries are connected in parallel t

ELECTRICAL CURRENT The movements of electrons along the conductor in a particular direction produce an electric current. The more electrons which move the greater the current. AMPERE : The amount of electron flow is the current and the current is measured in amperes. One ampere of current is said to flow when 6.28 x 10^18 electrons pass a given point in the conductor during a period of one second. The electric current or amperes (abbreviated amps) is measured by an ammeter.   DIRECT AND ALTERNATING CURRENT :  If the electrons flow continuously in one direction along the conductor, the current is said to be direct current (abbreviated d.c.). This is the type of current produced by a battery or a d.c. generator. If the electrons flow in one direction and then flow back again and continue this back and forth motion, the current is said to be alternating current (abbreviated a.c.). This is the type of current produced by an alternator or a.c. generator and is the type of electricity found