13 Direct current circuits

Question 1

internal resistance

Answer 1

resistance inside a source of electrical energy, loss of pd per unit current in the source when current passes through it

e= IR + Ir

Question 2

electromotive force (emf)

Answer 2

the amount of electrical energy per unit charge produced inside a source of electrical energy

e = E/Q

Question 3

potential divider

Answer 3

two or more resistors in series connected to a source of pd

Question 4

components in series rules

Answer 4

the current entering a component is the same as the current leaving the component
the current passing through two or more components in series is the same through each components

at any junction in a circuit, the total current leaving the junction is equal to the total current entering the junction

Question 5

potential difference rules

Answer 5

for two or more components in series, the total pd across all the components is equal to the sum of the potential differences across each component

pd across components in parallel is the same

for any complete loop of a circuit, the sum of the emus round the loop is equal to the sum of the potential drops around the loop

Question 6

resistors in series

Answer 6

R = R1 +R2 +R3 …

Question 7

resistors in parallel

Answer 7

1/R = 1/R1 + 1/R2 + 1/R3

Question 8

resistance heating

Answer 8

rate of heat transfer
I^2R
(energy per second transferred to the component as thermal energy)

Question 9

power supplied by the cell

Answer 9

Ie = I^2R + I^2r

R=r
maximum power is delivered to the load when the load resistance is equal to the internal resistance of the source

Question 10

measurement of internal resistance

Answer 10

V = e - Ir

Question 11

cell current

Answer 11

cell emf / total circuit resistance

Question 12

pd across each resistor in series with the cell

Answer 12

current x the resistance of each resistor

Question 13

current through each resistor

Answer 13

pf across the parallel combination/ resistors’s resistance

Question 14

Diodes

Answer 14

forward pd of 0.6 V

reserved current = infinite

Question 15

kirchoff’s laws

Answer 15

at any junction in a circuit, the total current entering the junction is equal to the total current leaving the junction

for any complete loop in the circuit, the sum of the emus around the loop is equal to the sum of the potential drops around the loop

Question 16

what a potential divider can be used for

Answer 16

supply a pd which is fixed at nay value between zero and the source pd
variable pd
supply a pd that varies with a physical condition such as temperature or pressure
light dependent resistor ( LDR)

Question 17

temperature sensor

Answer 17

consist of a potential divider divider mass using a thermistor and a variable resistor

Question 18

light sensor

Answer 18

uses a light-dependent resistor and a variable resistor

Question 19

power equations

Answer 19

P= IV
= I^2 R
= V^2 / R

Question 20

energy equation

Answer 20

E= IVt

Question 21

in dc circuits ….. and …. are conserved

Answer 21

energy and charge

Question 22

potential divider

Answer 22

used to supply constant or variable potential different from a power supply

Question 23

emf

Answer 23

The electromotive force (emf) is the potential difference of a source when no current is flowing

Question 24

Terminal voltage

Answer 24

Terminal voltage is the voltage output of a device is measured across its terminals. Terminal voltage is calculated by V = emf - Ir