diff --git a/Grade 9/Science/SNC1DZ/Unit_4_Physics_Study_Sheet.md b/Grade 9/Science/SNC1DZ/Unit_4_Physics_Study_Sheet.md
index 02f93af..16c3cfc 100644
--- a/Grade 9/Science/SNC1DZ/Unit_4_Physics_Study_Sheet.md	
+++ b/Grade 9/Science/SNC1DZ/Unit_4_Physics_Study_Sheet.md	
@@ -288,6 +288,20 @@
     - `Everything` has resistance. Conductor has low resistnace. Insulator has high resistance.
         - Example: wire has an resistnace so low that it is ignored in many calculations.
 
+## Factors Affecting The Resistance of Wires
+- ### 1. Type of Material
+    - Copper has much less resistance than iron.
+    - **Analogy**: Water flowing through a pipeful of gravel. Resistance depends on type of gravel.
+- ### 2. Length of Wire
+    - `Longer` wires have more resistance.
+    - **Analogy**: Water flowing through a pipeful of gravel. Resistance depends on length of pipe.
+- ### 3. Thickness 
+    - `Narrower` wires have more resistance.
+    - **Analogy**: Water flowing through a pipeful of gravel. Resistance depends on diameter of pipe.
+- ### 4. Temperature
+    - `Higher temperature` gives more resistance (More particles moving around and blocking it).
+    - A hot filament has more resistance tahn a cold filament because atoms in the hot filament vibrate more and the vibration increases the resistance.
+
 ## Product Efficiencies
 - Simply take the output / input x 100 and you get the percentage of the efficiency of your product.
 
@@ -300,10 +314,33 @@
 - $`I_T = I_1 = I_2 = I_3 \cdots = I_N`$
 - $`V_T = V_1 + V_2 + V_3 \cdots + V_N`$
 - $`R_T = R_1 + R_2 + R_3 \cdots + R_N`$
+- As **MORE** loads are added:
+    - $`R_T`$ `increases` because more loads are added.
+    - $`I_T`$ `decreases` because $`R_T`$ increases.
+    - $`I_{load}`$ `decreases` because voltage and resistance are the same for each load. 
+    - $`V_{load}`$ `decreases` because each load gets `less` voltage ($`V`$) ($`V_T`$ supplied by battery gets divided by more loads).
+    - Each light bulb has the `less brightness` **(because brightness depends on voltage)** (Less energy gets converted into heat and light in each light bulb).
 
 ## Parallel Circuits
 - In a parallel circuit, there are also a set of rules where the current, voltage, and resistance follow. The current and voltage rules are swapped in this case.
 - $`I_T = I_1 + I_2 + I_3 \cdots + I_N`$
 - $`V_T = V_1 = V_2 = V_3 \cdots = V_N`$
-- $`R_T = R_1^{-1} + R_2^{-1} + R_3^{-1} \cdots + R_N^{-1}`$ (I think).
-- $`R_T = (R_1*R_2)/(R_1 + R_2)`$
\ No newline at end of file
+- $`R_T = (R_1^{-1} + R_2^{-1} + R_3^{-1} \cdots + R_N^{-1})^{-1}`$ (I think).
+- $`R_T = (R_1 \times R_2)/(R_1 + R_2)`$
+- As **MORE** loads are added:
+    - $`R_T`$ `decreases` because more loads are added.
+    - $`I_T`$ `increases` because $`R_T`$ decreases.
+    - $`I_{load}`$ `stays the same` because voltage and resistance are the same for each load. 
+    - $`V_{load}`$ `stays the same` because each load gets the same voltage as before.
+    - Each light bulb has the `same brightness` **(because brightness depends on voltage)**.
+
+## Comparing Series And Parallel Circuits
+
+|Series Circuits|Parallel Circuits|
+|:--------------|:----------------|
+|- An electric circuit in which the compoenents are arranged one after another. <br>- It has only `one` path along which electrons can flow.<br>- If that path is interrupted, the whole circuit `stops`.|- An electric circuit in which the parts are arranged so that electrons can flow along `more` than one path. <br>- An interruption in one path `does not affect` the other path in the circuit|
+|**Voltage (V):**<br>- Total voltage is determined by the battery used<br>- Each load uses `portion` of the total voltage supplied by the battery<br>- As the number of loads `increases`, the potiental difference (voltage) for each load `decreases`|**Voltage (V):**<br>- Total voltage is determined by the battery used<br>- Voltage across parallel resistors will always be `the same`, even if the resistors have `different` values<br>- As the number of loads `increases`, the potiental difference (voltage) for each load `stays the same`|
+|**Current (I):**<br>- The current is the `same` throughout a series circuit<br>- As the number of loads `increases`, the total current `decreases`|**Current (I):**<br>- Each load uses `portion` of the total current from the battery<br>- As the number of loads `increases`, the total current `increases`|
+|**Resistance (R):**<br>- Total resistance `increases` when more resistors / loads are added<br>- As the number of loads `increases`, the total resistance `increases`|**Resistance (R):**<br>- Total resistance `decreases` when more resistors / loads are added<br>- As the number of loads `increases`, the total resistance `decreases`|
+
+