Predict/Calculate A light beam traveling in the negative z direction has a magnetic field B → = ( 3.02 × 10 − 9 T ) x ^ + ( − 5.28 × 10 − 9 T ) y ^ at a given instant of time. The electric field in the beam has a magnitude of 1 82 N/C at the same time. (a) Does the electric field at this time have a z component that is positive, negative, or zero? Explain. (b) Write E → in terms of unit vectors.
Predict/Calculate A light beam traveling in the negative z direction has a magnetic field B → = ( 3.02 × 10 − 9 T ) x ^ + ( − 5.28 × 10 − 9 T ) y ^ at a given instant of time. The electric field in the beam has a magnitude of 1 82 N/C at the same time. (a) Does the electric field at this time have a z component that is positive, negative, or zero? Explain. (b) Write E → in terms of unit vectors.
Predict/Calculate A light beam traveling in the negative z direction has a magnetic field
B
→
=
(
3.02
×
10
−
9
T
)
x
^
+
(
−
5.28
×
10
−
9
T
)
y
^
at a given instant of time. The electric field in the beam has a magnitude of 1 82 N/C at the same time. (a) Does the electric field at this time have a z component that is positive, negative, or zero? Explain. (b) Write
E
→
in terms of unit vectors.
3.) The graph shows how current I varies with potential difference V across a component X.
904
80-
70-
60-
50-
I/MA
40-
30-
20-
10-
0+
0
0.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
VIV
Component X and a cell of negligible internal resistance are placed in a circuit.
A variable resistor R is connected in series with component X. The ammeter reads 20mA.
4.0V
4.0V
Component X and the cell are now placed in a potential divider circuit.
(a) Outline why component X is considered non-ohmic. [1]
(b(i)) Determine the resistance of the variable resistor. [3]
(b(ii)) Calculate the power dissipated in the circuit. [1]
(c(i)) State the range of current that the ammeter can measure as the slider S of the potential divider
is moved from Q to P. [1]
(c(ii)) Describe, by reference to your answer for (c)(i), the advantage of the potential divider
arrangement over the arrangement in (b).
1.) Two long parallel current-carrying wires P and Q are separated by 0.10 m. The current in wire P is 5.0 A.
The magnetic force on a length of 0.50 m of wire P due to the current in wire Q is 2.0 × 10-s N.
(a) State and explain the magnitude of the force on a length of 0.50 m of wire Q due to the current in P. [2]
(b) Calculate the current in wire Q. [2]
(c) Another current-carrying wire R is placed parallel to wires P and Q and halfway between them as shown.
wire P
wire R
wire Q
0.05 m
0.05 m
The net magnetic force on wire Q is now zero.
(c.i) State the direction of the current in R, relative to the current in P.[1]
(c.ii) Deduce the current in R. [2]
2.) A 50.0 resistor is connected to a cell of emf 3.00 V. The voltmeter and the ammeter in the circuit are ideal.
V
A
50.00
(a) The current in the ammeter is 59.0 mA. Calculate the internal resistance of the cell.
The circuit is changed by connecting another resistor R in parallel to the 50.0 resistor.
V
A
50.00
R
(b) Explain the effect of this change on R is made of a resistive wire of uniform cross-sectional area 3.1 × 10-8 m²,
resistivity 4.9 × 10-70m and length L. The resistance of R is given by the equation
R = KL
where k is a constant.
(b.i) the reading of the ammeter. [2]
(b.ii) the reading of the voltmeter. [2]
(c) Calculate k. State an appropriate unit for your answer. [3]
[2]
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