Your circuit used the 220 Ω resistor. Now let's try the 1000 Ω resistor.

• Look down at the top of the LED’s dome and note its brightness.
• Replace the 220 Ω resistor with a 1000 Ω resistor.  In other words, replace the red-red-brown resistor with the brown-black-red resistor.  

The LED should be noticeably dimmer.

• Pull the 1000 Ω resistor out of the breadboard and put the 220 Ω resistor back in, and the LED should be back to normal brightness.
• Explain how the resistance affects the current through the circuit, which in turn affects the light’s brightness.