Describe how the students could build an electromagnet. Include in your answer how the students should vary and test the strength of their electromagnet. Flashcards
Details of how to make an electromagnet • wrap the wire around the nail • connect the wire to the power supply (with connecting leads and croc clips) Details of how to vary the strength of the electromagnet • change the number of turns (on the coil) • change the current (through the coil)
make an electromagnet
• wrap the wire around the nail
• connect the wire to the power supply (with
connecting leads and croc clips)
vary the strength of the electromagnet
• change the number of turns (on the coil) • change the current (through the coil)
test the electromagnet
• suspend paperclips from the electromagnet
• the more paperclips suspended, the stronger the
electromagnet is
• clamp the electromagnet at different distances from
the paperclip(s)
• the further the distance which paperclips can be attracted the stronger the electromagnet is
Electric Charge
Electrical current is the flow of electric charges. For an electric charge to flow there are two essential factors:
Potential difference.
Closed (or complete) circuit.
Electric current is measured in amperes (A). A current has the same value at every point in a single closed loop.
Give two essential factors for electric charge to flow:
Potential difference
Closed circuit
Current is used in the following equation for calculating the flow of charge:
Flow of charge (C) = current (A) x time (s)
The equation is also written as:
Q = It
What unit is electric current measured in?
Amperes
Potential difference is the difference in the amount of energy that charge carriers have between two points in a circuit.
The energy is transferred to the electrical components in a circuit when the charge carriers pass through them.
Charge
Charge= current * time
10 A of current flow through a wire for 2 seconds. What is the total charge transferred?
1 Remember the equation for charge Q = It 2 Substitute values Q = 10 × 2 3 Calculate and remember the unit Q = 20 C
POTENTIAL DIFFERENCE
Potential difference is measured in volts (V) and is also called voltage. Potential difference can be calculated in the following equation:
Potential difference (V) = current (A) × resistance (Ω) V = IR
What is potential difference?
The difference between the amount of energy between 2 points in a circuit
VOLT METERS
Voltmeters measure the potential difference (or voltage) between two points in a circuit.
Voltmeters must always be connected in parallel (on a separate branch of the circuit) with the two points being measured.
What is the symbol equation for calculating potential difference?
V=IR
VOLTMETER
MUST ALWAYS BE CONNECTED IN A PARRALLEL
MEASURE POTENTIAL DIFFERENCE
SERIES CIRCUITS
A series circuit has all its components connected on the same line as each other.
ONE CONTINIOUS LOOP
In a series circuit, the current is the same at all points in the circuit.
How is a resistor drawn in a circuit diagram?
A box with a line on either side
The charge flows through the circuit like water flows through pipes.
The amount of water entering one end of a pipe is the same as the amount leaving the other end.
If the current at R1 in a series circuit is 5 A, what is the current at R2 in the same series circuit?
5A
In series circuits, the resistors all oppose the flow of electric current through the circuit.
The total resistance in a series circuit is calculated by adding up the resistance of each individual resistor.
E.g. R = R1 + R2 + R3
What is the role of resistors in a series circuit?
Oppose the flow of electric current
How is a bettery madE?
A battery is made by joining cells together.
In a series circuit, R1 = 1 Ω and R2 = 1 Ω. What is the total resistance?
2
The total e.m.f. (energy that drives a current to flow through a circuit) in a series circuit is found by adding up individual electromotive forces (e.m.f) of the cells in the circuit.
E.g. E = E1 + E2 + E3
