Understand that the true and false state correspond to two distinct voltage levels. Realize that these two states include the battery supply voltage level, often 5 volts, known as the true state, and the battery ground voltage level, often 0 volts, known as the false state.
Analyze the NOT gate's logic operation. Use a logic simulator or breadboard--an actual NOT gate. Place 5 volts on the input of a NOT gate. Record the voltage at the output of the NOT gate. Conclude that when 5 volts is applied to the input of a NOT gate, the NOT gate produces a voltage of 0 volts at its output.
Now apply a voltage of 0 volts on the input of the NOT gate. Record the voltage at the output of the NOT gate. Conclude from your measurement that when 0 volts is applied to the input of a NOT gate, the NOT gate produces 5 volts at its output.
Analyze the operation of a two-input OR gate. Use a logic simulator or breadboard--an actual OR gate. Apply the 0 volts to both inputs of the OR gate. Record the resultant output voltage of the OR gate. Conclude that when both the inputs of the OR gate are at 0 volts, the output of the OR gate is also at 0 volts.
Apply 0 volts to one input of the OR gate and 5 volts to the other input of the OR gate. Record the output voltage of the OR gate. Interchange the voltages on the input pins of the OR gate. Conclude that when one input of the OR gate is at 0 volts, and the other input is at 5 volts, the output of the OR gate will be at 5 volts.
Apply 5 volts to both inputs of the OR gate. Record the output voltage of the OR gate. Conclude that when both inputs of an OR gate are at 5 volts, the output of the OR gate will be 5 volts.
Conclude that for a two-input OR gate, the output voltage will only be at 0 volts when all the inputs of the OR gate are also at 0 volts. Also conclude that if one or more inputs of the OR gate is equal to 5 volts, the output of the OR gate will also be equal to 5 volts.