P3.2 Simple Circuits

Question 1

What happens to resistance of thermistor as temperature increases

Answer 1

Thermistor’s resistance decreases
OPPOSITE TO NORMAL RESISTORS

Question 2

Switch circuit symbol

Answer 2

Open
-o o-
. \

Closed
-o—o-

Question 3

Circuit symbol for a lamp

Answer 3

—⨂—

Question 4

Circuit symbol for a fuse

Answer 4

⏛

Question 5

Voltmeter circuit symbol

Answer 5

—Ⓥ—

Question 6

Circuit symbol for an ammeter

Answer 6

—Ⓐ—

Question 7

Diode

Answer 7

. ___
—(▷I)—
. ‾‾‾‾
Current only flows in one direction.
Resistance is very high in the other direction, preventing current flow

Question 8

Resistor circuit symbol

Answer 8

—▭—

Question 9

Thermistor circuit diagram

Answer 9

. /
—▭—
. _/

Question 10

Circuit symbol for a variable resistor

Answer 10

—↗—

Question 11

LDR

Answer 11

↘↘
. —(▭)—

Used in street lamps or night lights.
When light levels become low enough, the light gains sufficient current to turn on

Question 12

LED circuit symbol

Answer 12

.↗️↗️
—▹|—

Question 13

Series circuit

Answer 13

Same charge passes through all components,
so current through each component is same.

Voltage is SPLIT

Question 14

Parallel circuit

Answer 14

Circuit in which the charge is split between branches

Current is SPLIT between branches

Question 15

2 factors current in a circuit depends on

Answer 15

Potential Difference (V)
Resistance (R)

Question 16

Equation to calculate potential difference if current and resistance are known

Answer 16

V = IR
Potential Difference (V), Current (A),
Resistance (ohms)

Question 17

Ohmic Conductor and conditions required

Answer 17

Conductor for which current and potential difference are directly proportional

Resistance remains constant as current changes
Temperature must be constant

Question 18

4 components for which resistance is not constant as current changes.

Answer 18

Lamps
Diodes
Thermistors
Light Dependant Resistors (LDRs)

Question 19

What happens to resistance of a filament lamp as temperature increases

Answer 19

Resistance increases

Ions in metal have more energy, so vibrate more, causing more collisions with electrons as they flow through the metal, creating greater resistance

Question 20

Examples of when a thermistor may be used

Answer 20

In a thermostat to turn a heater on below a certain temperature
In a freezer to turn on a cooler when the temperature becomes too high.

Question 21

State what happens to resistance of a LDR as light intensity decreases

Answer 21

LDR’s resistance increases

Question 22

2 ways that a component can be connected in a circuit

Answer 22

Series (same loop)
Parallel (adjacent loop)

Question 23

How potential difference across components varies when connected in series and parallel

Answer 23

Series: Total PD is SPLIT between each component

Parallel: PD across each component is same

OPPOSITE FOR CURRENT

Question 24

If 2 resistors are connected in PARALLEL, what can be said about their combined total resistance?

Answer 24

Their total resistance is less than the smallest of the two individual resistances

Question 25

If 2 resistors are connected in series, what can be said about their total resistance?

Answer 25

Their total combined resistance is equal to sum of the 2 individual resistances

Question 26

Equations for power of a circuit

Answer 26

P = I V
P = 1²R
Power (Watts), Current (Amperes), Potential Difference (Volts), Resistance (Ohms)

Question 27

Equation linking energy transferred, power and time

Answer 27

E = Pt
Energy (Joules), Power (Watts), Time (Seconds)

Question 28

Equation linking energy transferred, power and time

Answer 28

E = QV
Energy (Joules), Charge (Coulombs), Potential Difference (Volts)
Energy = power

Question 29

How a voltmeter should be connected in a circuit

Answer 29

In parallel to component that you are measuring the potential difference for

Question 30

How an ammeter should be connected in a circuit

Answer 30

In series with the branch you are measuring the current for