01 electric quantities (solving)

Question 1

Formula

Current (I)

Answer 1

I = Q/t

𝑰 = current (ampere)
𝑸 = charge (coulomb)
𝒕 = time (second)

Question 2

Formula

Current

Answer 2

I = V/R

Ohm’s Law

Question 3

Formula

Voltage (V)

Answer 3

V = IR

Question 4

Formula

Voltage (V)

Answer 4

V = E/Q

𝑽 = voltage (volt)
𝑬 = energy (joule)
𝑸 = charge (coulomb)

Question 5

Resistance (R)

Answer 5

𝑹 =𝝆𝑳/𝑨

𝑹 = resistance (ohm)
𝝆 = resistivity (ohm-meter)
𝑳 = length (meter)
𝑨 = cross-sectional area (m2)

Question 6

Formula

Resistance

Answer 6

R = V/I

Question 7

Formula

Electric Power

Answer 7

P = VI
P = E/t

E = energy
t = time

Question 8

Sample Problem

How much electric charge passes through a 9-ampere
instrument within 2 minutes?

Answer 8

1080 C

Question 9

Sample Problem

A portable Bluetooth speaker is powered by a 5-volt
USB source. If the speaker draws a total charge of
120 C while playing “Buksan Mo”, how much energy
has been transferred to the device?

Answer 9

600 J

Question 10

Sample Problem

An electric motor uses 450 joules of energy to move
30 coulombs of charge through a circuit. What is the
potential difference across the motor?

Answer 10

15 V

Question 11

Sample Problem

A spool contains 250 m of copper wire with a total
resistance of 10 Ω . If a technician needs to create a
component with a resistance of exactly 8 Ω, how many
meters of wire must be used?

Answer 11

200

Question 12

Sample Problem

A hair dryer has an internal resistance of 15 Ω. If it is
plugged into a standard 110-V wall outlet, how much
current will flow through the device?

Answer 12

7.33 A

Question 13

Sample Problem

A decorative LED light strip is connected to a 12-V DC
power supply. If the light strip draws a current of 0.4 A,
what is the total electrical resistance of the LED strip?

Answer 13

30 Ω

Question 14

Sample Problem

A small sensor in an electronic circuit operates at a
voltage of 12 V. When the sensor is active, a current of
30 mA flows through it. What is the electrical resistance
of this sensor?

Answer 14

400 Ω

Question 15

Sample Problem

A localized heating element in a coffee machine is rated
at 600 W. It draws a current of 4 A when running. What
is the electrical resistance of the heating element?

Answer 15

37.5 Ω

Question 16

Sample Problem

An electric microwave oven is rated at 1.10 kW. When it
is running, it draws a current of 5 A. What is the voltage
of the power source it is connected to?

Answer 16

220 V

Question 17

Formula

Conductance

Answer 17

G = 1/R