Circuit Basics
Which of the following is required for current to flow in a circuit?
a) Open switch
b) Insulator
c) Closed circuit
d) Resistor only
C- Closed circuit
Which equation gives electrical power?
a) P = IV
b) P = V/I
c) P = R/V
d) P = I + V
A- P = IV
Which factor does NOT affect electrical energy used?
a) Current
b) Voltage
c) Resistance
d) Time
C- Resistance
Which device converts electrical energy into motion?
a) Speaker
b) Fan
c) Bulb
d) Heater
B- Fan
In a series circuit, the total resistance increases as more resistors are added because the current has only ______ path to follow.
One
An appliance operating at high current and low voltage may have the same power as one operating at low current and ______ voltage.
High
To calculate the total energy used by a device over time, both the rate of energy transfer and the ______ of operation must be considered.
Duration
A device with a low power rating may still consume a lot of energy if it is used for a ______ period of time.
Long
Electricity is created inside the bulb.
❌False
Reason: Electricity is not created inside the bulb; it is supplied to the bulb from an external source, like a battery or the mains (wall socket).
If two devices operate at the same voltage, the one with higher resistance will have higher power output.
❌ False
Reason: More resistance limits how much energy flows per second; so even if the voltage is the same, higher resistance means less power, not more (P = V2/R)
A 100 W device uses the same amount of energy in 10 seconds as a 200 W device in 5 seconds.
✅ True
Reason: E = Pt → 100×10 = 200×5 = 1000 J
A phone charger consumes more power than an electric kettle.
❌ False
Reason: Kettles have higher power ratings than phone chargers.
What component provides energy to a simple circuit?
Battery or Cell
Calculate the electrical power supplied to a 12V electrical heater when the current passing through it is 3.0A.
V=12 V, I=3.0 A
P=IV
P= 3.0×12
P= 36W
The reading on the ammeter is 2.4A, and the reading on the voltmeter is 14V. Calculate how much energy transferred by the resistor in 15s.
I=2.4 A, V=14 V, t=15 s
E= IVt
E= 2.4×14×15
E= 504J
How much energy does a 500 W heater use in 2 minutes?
P=500 W, t=2 minutes=120 s
E=P×t
E= 500×120
E= 60,000 J
I shine without burning, I help you see. What am I?
Bulb
I balance volts and current as they glide; I shift with the load and never hide.
Resistance
I balance volts and current as they glide; I shift with the load and never hide.
Electrical Work
I move air without burning fuel.
Fan