I'm trying to power a linear actuator through the 5v pin and when I power the Arduino Uno with a USB-C cable connected to my laptop, the actuator starts making a ticking noise and it doesn't work. I'm assuming this happens because the actuator isn't receiving enough power. However, when I power the Arduino Uno with a 9v battery, the actuator seems to function properly. I don't know why this happens but I'd like to understand why.
Never power inductors from the Arduino 5v pin.
Use an external power supply and an appropriate power driver controlled by the Arduino.
Are you saying that the linear actuator is a form of an inductor?
Linear actuators are a form of electric motor, thus an inductor.
USB only supplies 500mA, 9V battery can supply more - for a little while ...
larryd:
Never power inductors from the Arduino 5v pin.Use an external power supply and an appropriate power driver controlled by the Arduino.
Can I ask why I shouldn't be powering the linear actuator with the 5v pin? I'm using the one from the link below and putting the 5v in the red wire, the ground in the black wire, and a separate input pin on the Arduino Uno for the white wire. It seems to me that the servo was meant to be wired this way.
https://www.actuonix.com/L12-R-Linear-Servo-For-Radio-Control-p/l12-r.htm
As Crossroards said, USB is limited in the current supplied to ~500mA.
If you were to power the Arduino thru the power jack current out on the 5v pin is even less than 500mA.
Motors, relays and other inductive loads generate large voltage spikes which can damage the USB power source or 5v regulator and other components on the Arduino.
Whenever you need to power a high current load, whether inductive or resistive, you ‘must’ use an external power source that is designed to handle large current loads.
Inductive loads must have conditioning to prevent voltage spikes from damaging near by electronics.
Hi,
This may help;
Can you please tell us your electronics, programming, arduino, hardware experience?
Tom... 
kylekam:
Can I ask why I shouldn't be powering the linear actuator with the 5v pin?
The 5V supplies logic and sensor IC's, all of which are easily destroyed by overvoltage, and can mis-behave if
their supply voltage isn't constant and clean of spikes.
Inductive loads can generate 100V+ spikes (especially if the circuit's misdesigned), and motors in particular
are very low resistance until they spin up, pulling lots of current (amps), which often crow-bars the supply
voltage down towards ground momemtarily. None of this is safe for IC power rail.
Separate power for logic and inductive or high current loads is always preferred.
TomGeorge:
...Can you please tell us your electronics, programming, arduino, hardware experience?
Tom...
I have a high school level of understanding of circuits but beyond that I'm completely brand new to arduino, electronics, and hardware.