Resistors come in different sizes and colors to indicate their resistance values. The last color band on a resistor, usually gold or silver, indicates the tolerance of the resistor. To calculate a resistor's value, identify the color bands from right to left and write down the corresponding digits, placing the appropriate number of zeroes after the last digit based on its band's color. Breadboards are used to prototype circuits without permanent connections. They contain rows of metal strips that allow components to be connected easily and tested without soldering. Circuit diagrams use symbols to represent components and show how they are connected to form a working circuit.