Electric circuits

• How does a material become negatively charged?

  becomes negatively charged by GAINING electrons
• How does a material become positively charged?

  becomes positively charged by LOSING electrons
• If two objects that are positively charged come close to each other what happens?

  Repel each other

  
• If two objects that are negatively charged come close to each other what happens?

  Repel each other

  
• If two objects have opposite charges and come close to each other what happens?

  Attract each other

  
• What is an electric field?

  Region in which electrically charged particles experience a force.
• What happens to the strength of an electric field as you get further from the charged object?

  It decreases
• Electric current?

  Flow of charge
• Unit of charge?

  Coulomb (C)
• Unit of current?

  Ampere (A)
• Unit of time?

  second (s)
• Equation for potential difference (voltage)

  $V=$$IR \hspace{10mm} Voltage =$$Current \times Resistance$
• Voltage in series circuit

  $V_1+$$V_2=$$V_{total}=$$V_{supply}$
• Resistance in series circuit

  $R_{total}=$$R_1+$$R_2+$$R_3+$$...$
• Current in parallel circuit

  Current splits into different branches. $I_{total}=$$I_1+$$I_2+$$I_3+$$...$

  
• Voltage in parallel circuit

  Same everywhere. $V_1=$$V_2=$$V_3=$$V_{supply}$

  
• Resistance in parallel circuit

  Adding more resistors, decreases total resistance. $\dfrac{1}{R_{total}}=$$\dfrac{1}{R_1}+$$\dfrac{1}{R_2}+$$\dfrac{1}{R_3}+$$...$

  
• Current in series circuit

  Current in series circuit same at all points. $I_1=$$I_2=$$I_3=$$I_{supply}$
• What happens to resistance of a filament lamp as temperature increases?

  Resistance increases
• What happens to resistance of thermistor as temperature increases?

  Resistance decreases

  
• What happens to the resistance of a light dependent resistor when light intensity increases?

  Resistance decreases

  
• I-V graph for resistor

  straight line with gradient 1/R

  
• I-V graph for diode

  Current zero for negative potential difference. I-V graph curves upwards means resistance is decreasing.

  
• I-V graph for filament bulb

  current increases to a certain point then increases more slowly