3. D.C. Circuits

Question 1

Tell me all about current in a series circuit

Answer 1

• Current stays the same throughout all components
• But changes based on number of components or voltage
• +V = increases, +components = decreases

Question 2

Tell me all about current in a parallel circuit

Answer 2

• Current splits at a junction
• Largest currents will flow to path w/ least resistance
• Sum of current after split (junction) is equal to current before
• But current is distributed evenly technically tho be aware of 2nd point

Question 3

What’s Kirchoff’s 1st law

Answer 3

At a junction in a circuit, the sum of the currents entering the junction is equal to the sum of the currents leaving the junction

Question 4

Define EMF (electro motive force)

Answer 4

The energy converted from chemical energy to electrical potential energy

Question 5

Define PD (potential difference)

(2 definitions)

Answer 5

The difference in electrical potential energy at 2 different points

The energy converted from electrical potential to other forms

Question 6

How to find work done in a circuit
(not in data booklet)!!!

Answer 6

J = v x c
Work done = voltage x charge

Question 7

Tell me all about voltage in a series circuit

Answer 7

• P.D splits between components
• Larger resistance = more P.D (ohms law)
• Sum of P.D in series = EMF of the supply

Question 8

Tell me all about voltage in a parallel circuit

Answer 8

P.D is the same for components in parallel loops regardless

Question 9

What’s Kirchoff’s 2nd law

Answer 9

In any closed loop in a circuit, the sum of the emf’s is equal to the sum of the pd’s around the loop

Just look at their own individual loops

Question 10

Tell me the EMF of a cell

Answer 10

The quantity of energy each coulomb of charge can receive from the cell. Chemical to electrical energy

The chemical energy converted to electrical potential energy per unit charge
^^ this is better

Question 11

Tell me the PD of a cell

Answer 11

Quantity of energy that each coulomb of charge transfers in the circuit. Electrical to other forms of energy

Electrical energy converted to other forms of energy per unit charge
^^ 50/50

Question 12

How do u find total resistance in a series

Answer 12

Add them

Question 13

How do u find total resistance in a parallel

Resistance at top is 100 ohms and resistance and bottom is 500 ohms?

Answer 13

1/Rtotal = 1/100 + 1/500 = 5/500 + 1/500 = 6/500

Rtotal = 500/6 = 83.3 Ohms

• So u need to make the 100Ω equal with the 500Ω as the denominator
• Ofc, it affects the numerator as well
• Then after adding u actually do the dividing
• And vwallah

Question 14

What about best of both worlds for finding total resistance?

Answer 14

• Parallel first
• Then series
• Ez pz

Question 15

2 ways of finding voltage across each resistor?

Answer 15

Method #1:

• Use equation VIR
• Find total current by finding total resistances by adding n shi
• Then find voltage as u already got the main current

Method #2:
- Potential divider equation
- It’s in data booklet however u’ll need to rearrange (vin and vout one okay?)

Question 16

Explain thermistor in high temperatures in a circuit

Answer 16

High temperature:
- EMF is unchanged
- Rtotal decreases
- I increases as total resistance decreases
- V decreases as Rtotal/Rtotal+R decreases

Question 17

Explain thermistor in low temperatures in a circuit

Answer 17

Low temperature:
- EMF is unchanged
- Rtotal increases
- I decreases as total resistance increases
- V increases as Rtotal/Rtotal+R increases

Question 18

Use of a thermistor for everyday appliances type shi

Answer 18

A thermostat or fridge

Question 19

Explain LDR in day/night in a circuit?
And a use of this?

Answer 19

No light = resistance increases
Light = resistance decreases

Street lights