Electricity Flashcards
If the fan in the circuit below has a resistance of 8.0 Ohm’s and needs at least 4.0v to work properly, calculate the minimum amount of current that needs to flow through the fan so that it works correctly.
V=IR Voltage= current x resistance 4.0V= current x 8.0 ohm's Current= 4.0/8.0 Current= 0.5A
The minimum amount of current that needs to flow through the fan so that it works correctly is 0.5A.
Draw a fixed resistor
(rectangle with two lines coming from either end)
Draw an open switch
(two lines- one vertical and one open diagonal)
Draw a battery
(tall line, small line, dots, tall line, small line)
Describe the structure of a wire (safety etc)
A wire’s core is made of copper due to it being a good electrical conductor, and the outer of the wire is made of plastic because it is an electrical insulator.
Identify the difference between a conductor and insulator
Conductors have a low electrical resistance and allow electricity to flow through them. Insulators have a high electrical resistance and will not allow electricity to flow through them easily.
Relate the structure of a wire and the difference between a conductor and insulator to how the structure of a wire protects people
Because the outer layer of the wire is made of plastic, which is an electrical insulator, it keeps the electricity flowing through the wire into the circuit and makes it safe for you to touch the wire and not get an electrical shock.
Explain how a fuse can help switch off a device if an increase of current flows through it
Fuses are connected into circuits as a safety component. If the current gets too high, the fuse will break and disconnect the circuit. The fuse contains a piece of wire that melts easily. If the current going through the fuse is too great, the wire heats up until it melts and breaks the circuit. This prevents fires and electric shocks.
Where would you add a switch to a diagram to only turn the front lamp on and off?
sheet
Where would you add a switch to a diagram to turn both the front and back lamp on and off?
sheet
Where would you add an ammeter to a diagram to measure the current of the rear lamp only?
sheet
Where would you add an voltmeter to a diagram to measure the current of the front lamp only?
sheet
Determine the voltage across the speaker and then calculate the resistance of the speaker if a current of 0.25A flows through it and the voltage is 12V. Give your answers with the correct units.
V=IR Voltage= current x resistance 12V= 0.25A x resistance Resistance= 12/0.25 Resistance= 48 ohm's
Voltage is the same everywhere in a parallel circuit so 12 volts will pass across the speaker.
State the value of current and voltage through Bulb B. The current is 3.5A. Resistance for Bulb A is 2.0 ohm’s and Bulb B is 2.0 ohm’s.
Current is the same everywhere in a series circuit so the current flowing across Bulb B will be 3.5A.
V=IR Voltage= current x resistance Voltage= 3.5A x 4.0 ohm's 3.5 x 4.0= 14 volts Voltage is evenly divided between the bulbs so 14 volts divided by 2 bulbs= 7 volts.
Discuss the changes in current and voltage across each bulb and resistance in a series circuit if another bulb was added at point X (at the start of the circuit).
The current stays the same for every bulb in a series circuit, so there wouldn’t be a change in current if you added another bulb to point X. The voltage in a series current is divided evenly between the bulbs in the circuit so if you added another bulb the voltage for each individual bulb would decrease. For instance if there were 50 volts in the circuit, without another bulb at point X, there are only 10 bulbs, meaning 5 volts would be delivered to each bulb. If you added another bulb, that would mean there is 11 bulbs in the circuit and only 4.5 (approximately) will be delivered to each bulb.
