Potential difference is usually measured by an instrument called a voltmeter. The voltmeter is connected across the two points in a circuit between which potential differences are to be measured. It is necessary that the resistance of the voltmeter be large compared to the circuit resistance across which the voltmeter is connected. Otherwise an appreciable current will flow through the voltmeter which will alter the circuit current and the potential difference to be measured. Thus the voltmeter can read the correct potential difference only when it does not draw any current from the circuit across which it is connected. An ideal voltmeter would have an infinite resistance.
However, there are some potential measuring instruments such as digital voltmeter and cathode ray oscilloscope which practically do not draw any current from the circuit because of their large resistance and are thus very accurate potential measuring instruments. But these instruments are very expensive and are difficult to use. A very simple instrument which can measure and compare potential differences accurately is a potentiometer. A potentiometer consists of resistor in the form of a wire on which a terminal can be slide.
Solar battery charger is the source of getting natural energy from the sun in order to charge our batteries. Generally people thinks that solar chargers and power inverters for cars are same things but they are not same and they perform different functions. Energy in solar battery chargers are powerful than power inverters for cars. And power inverters for cars are to change the current from one form to another using a car battery. We can say that power inverters are needed for these batteries to perform multi tasks. These battery chargers are found in different rates a wide range of these batteries are available in the market for all people to use.