This app shows a simple circuit containing one resistor. In addition there is a voltmeter (parallel to the resistor) and an ammeter (in series with the resistor).
You can select the maximum voltage and maximum amperage values tolerated by the meters by using the choose boxes. If you see the warning "Maximum exceeded!", you will have to choose an adequate measuring range. Resistance and voltage can be changed with the four buttons. The values of voltage (U) and amperage (I) are indicated on the bottom right.